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PAVEMENTS 


EXTERN  PAVIN 

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Text  Book  on  Brick  Pavements 

Price 31-50 

For  sale  by 
WESTERN  PAVING  BRICK  MFRS.  ASSN. 

G.  W.  Thurston.  Secretary 
416  Dwight  Building,       Kansas  City,  Missouri 


1 

Announcement 

IN  ISSUING  this  volume,  the  Western  Paving 

Brick  Manufacturers  Association  is  pursuing  one 

of  the  chief  aims  of  its  organization  —  the  educa- 

tion of  the  public  in  the  characteristics  and  proper 

construction  of  Vitrified  Brick  Highways  and  City 

Pavements. 

This  Association  endeavors  to  bring  about  a 

closer  relationship  between  the  public,  or  the  user, 

and  the  manufacturer,  realizing    a  satisfied  public 

means  securing  increased  business. 

It    is    believed    the   circulation  of  an    author- 

ative  Text  Book  written  by  an  Engineer  of  prom- 

inence, will  do  much  toward  improving  the  quality 

and  construction  of  Vitrified  Brick  Highways  and 

City   Pavements,   create     a    greater  interest    and 

demand  for  this  type  of  improvement,  and  establish 

additional  confidence  of  the  public. 

With^this  sole  purpose  in  view,  the  Association 

commends   this  Text  Book  to  those  who  are  inter- 

ested in  permanent  pavements. 

WESTERN  PAVING  BRICK 

MANUFACTURERS   ASSOCIATION, 

G.  W.  Thurston,  Secretary, 

416  Dwight  Building, 

Kansas  City,  Missouri. 

Brick  pavement! in  Holland  over  100  years  old. 


A  TEXT  BOOK 

ON 

BRICK   PAVEMENTS 

BY 

CLARK  R.  MANDIGO,  A.  B.,  M.  C.  E. 

(Associate  Member  American  Society  Civil  Engineers. 
Formerly  Assistant  City  Engineer,  Kansas  City,  Missouri.) 


WESTERN  PAVING  BRICK  MANUFACTURERS 
ASSOCIATION 

KANSAS  CITY,  MISSOURI. 

1917 


, 

>* 


COPYRIGHT 

1917 

BY 

CLARK  R.  MANDIGO 


PREFACE 

BJIGHWAY  ECONOMICS  have  advanced  so  rapidly  in  the  past 
fifteen  years  that  it  has  become  practically  impossible  to 
treat  fully  all  phases  of  the  subject  in  one  volume.  A  book  on 
street  pavements  alone  becomes  bulky  and  special  volumes  are 
necessary  to  cover  the  subjects  of  street  designs,  country  roads, 
street  cleaning,  etc.  The  increased  amount  of  traffic  due  to  the  rapid 
development  of  the  automobile  has  not  only  thrown  an  increased 
strain  on  street  and  road  pavements,  but  has  created  a  demand  for 
more  pavements  and  for  smoother  and  better  pavements  maintained  to 
a  high  degree  of  perfection. 

It  occured  to  the  writer  that  a  series  of  hand  books  treating  each 
of  the  standard  pavements  separately  would  perhaps  enable  them  to  be 
covered  in  a  comprehensive  manner  with  the  entire  emphasis  of  the 
subject  matter  on  the  particular  pavement  under  consideration.  In 
this  way  each  class  of  pavement  and  related  subjects  may  be  treated  in 
an  exhaustive  manner  with  the  view  to  obtaining  the  most  satisfactory 
final  pavement  surface  of  the  type  under  discussion.  There  must  of 
necessity  be  included  considerable  matter  applicable  to  all  the  stan- 
dard pavements  but  an  effort  has  been  made  to  exclude  from  this  vol- 
ume general  discussions  which  are  not  pertinent  to  brick  pavements. 

The  author  is  an  advocate  of  good,  well  constructed  pavements. 
He  believes  that  there  is  a  place  for  all  the  standard  paving  materials, 
provided  that  skill  and  care  are  used  in  the  design  and  construction. 
Greater  attention  to  details  and  a  more  thorough  understanding  of  the 
limitations  as  well  as  the  strong  points  of  each  kind  of  pavement  are 
essential  items  to  good  street  or  road  surfaces. 

It  is  hoped  that  the  present  volume  on  Brick  Pavements  will 
prove  of  interest  to  municipal  officers,  commissioners  and  citizens  in 
general  as  well  as  to  city  engineers,  road  engineers,  county  surveyors 
and  paving  contractors.  For  this  reason  many  tables,  formulae  and 
other  technical  matter  have  been  omitted  as  these  would  be  dry  read- 
ing for  the  first  class  of  readers  and  are  available  to  the  second  class 
in  numerous  published  handbooks  for  engineers. 

The  author  wishes  to  acknowledge  the  lielp  and  encouragement 
rendered  by  the  Western  Paving  Brick  Manufacturers  Association  in 
the  preparation  of  this  volume.  They  have  undertaken  its  publica- 
tion and  distribution  and  otherwise  aided  in  gathering  the  illustra- 
tions and  historical  data.  Their  interest  in  the  subject  matter  has 
been  the  presentation  of  methods  of  construction  which  will  insure 
the  best  and  most  satisfactory  use  of  brick  material  for  pavements. 
August,  1916  CLARK  R.  MANDIGO. 

Kansas  City,  Missouri. 


365557 


TABLE  OF  CONTENTS 

CHAPTER  1.    BRICK  PAVEMENTS. 

Development  of  pavements — Ancient  pavements — Various  materials 
used — Survival  of  Standard  pavements.  History  Brick  pavements 
— Durability  of  old  brick  pavements — present  use  brick.  Ad- 
vantages of  brick  pavements.  Pages  9  to  18. 

CHAPTER  II.    HIGHWAY  ECONOMICS. 

Advantages  paved  roads — tangible — intangible.  Advantages  paved 
streets.  Rolling  resistance.  Grade  resistance.  Location  roads. 
Fixing  grades.  Location  of  and  grades  on  streets.  Pages  19  to  30. 

CHAPTER  III.     THE   SUB-GRADE   AND   FOUNDATION. 

Importance  of  sub-grade  work.  Capacity  culverts.  Design  cul- 
verts. Brick-arch  culverts — Bridges.  Grading — Cuts  and  fills, 
surface  drainage.  Sub-drainage,  object,  methods.  Object  rolling 
subgrade.  Purposes  of  foundation.  Concrete  foundation — ma- 
terial, mixing,  placing,  templets,  curing.  Summary.  Pages  31  to  42. 

CHAPTER  IV.  MANUFACTURE  OF  BRICK. 

Development  of  industry.  Shales  and  Clays,  Occurence,  Plas- 
ticity, Impurities.  Grinding,  dry  pan,  screens.  Tempering,  pug- 
mill,  augur  machine,  moulding,  forms,  die.  Internal  structure, 
spiral  layers,  laminations.  Vertical  Fiber  Brick.  Die,  lining,  shape, 
lubrication.  The  clay  column.  Cutting  Table.  Repress — action 
on  clay  structure,  advantages,  disadvantages.  Wire  Cut  Brick, 
Dunn  type,  Vertical  Fiber  type,  advantages  each.  Drying  room. 
Kilns.  Three  stages  burning — steaming,  oxidizing,  vitrifying.  An- 
nealing. Testing  brick,  strength,  specific  gravity,  absorption.  Rat- 
tler Test,  method,  results,  advantages,  allowable  loss  for  various 
classes  pavements.  Uniformity  of  brick.  Plant  inspection.  Other 
tests.  Pages  43  to  60. 

CHAPTER  V.    LAYING  THE  BRICK. 

The  sand  cushion,  depth,  object.  Cement-sand  bed,  advantages, 
method  of  spreading.  Bedding  course,  quality  sand,  method 
spreading,  templet.  Laying  brick,  angle,  closures,  valve  boxes,  in- 
tersections. Handling  brick.  Brick  layers.  Rolling — method,  ob- 
ject. Readjustments.  Culling.  Joint  Fillers— sand,  grout,  bi- 
tuminous. Method  placing  grout  filler.  Expansion — amount,  effect, 
expansion  joints.  Method  placing  bituminous  filler,  surface-car- 
pet, expansion.  Advantages  and  disadvantages,  cement  grout  and 
asphalt  fillers.  Where  each  should  be  used.  Lugless  brick,  ad- 
vantages. Monolithic  brick  pavement — history,  method  laying, 
special  templet,  grouting,  on  city  streets.  Strength  tests  mono- 
lithic brick  slabs.  Advantages.  Maintenance — construction  de- 
fects, cost,  service  cuts.  Duties  engineer,  inspector,  contractor. 
Pages  61  to  86. 

CHAPTER  VI.    PAVING  PROBLEMS. 

First  cost  versus  ultimate  cost.  Qualities  ideal  pavement.  Scien- 
tific selection  of  pavements.  Traffic — weight,  speed,  impact  of 
automobile  loads.  The  automobile  tire — 3  methods  of  destruction 
of  road  surface.  Design,  widths  streets,  roads.  Pavement 
crowns — amount,  distribution.  Combined  curb  and  foundation. 
Radius  curb  at  corners.  Catch  basins,  valleys,  storm  drains. 
Sidewalks,  tree  space. 

Appendix  Standard  Specifications. 


CHAPTER  I 

BRICK  PAVEMENTS 

^DS  OF  SOME  KIND  are  essential  to  civilization  and  hard  sur- 
face roads  are  a  necessity  in  the  up-building  of  the  commercial 
and  social  features  of  a  progressing  community.  It  has  been 
well  said  that  roads  are  the  physical  system  by  which  to 
measure  the  progress  of  an  age  or  a  people.  Roads  are  so 
important  to  the  life  of  a  community  that  they  are  usually  the  first 
things  thought  of  in  any  new  colony.  First  there  is  the  trail,  then 
the  path,  the  road,  the  graded  earth  road  and  finally  the  paved  road; 
each  one  representing  a  step  of  progress  and  making  possible  larger  / 
centers  of  population  and  greater  social  and  commercial  activity.  x 

While  the  remarkable  growth  of  the  steam  railroad  in  the 
United  States  and  the  sparse  population  of  the  farm  land  has  lessen- 
ed the  importance  of  a  comprehensive  system  of  cross  country  paved 
roads,  the  local  roads  as  feeders  for  commercial  towns  and  railroads, 
are  as  important  as  formerly.  It  is  manifestly  impossible  to  con- 
struct a  railway  to  every  farm.  Pavements  are  desirable  at  any 
time  and  become  a  necessity  when  any  great  number  of  wheel 
vehicles  attempt  to  use  the  roads. 

The  Egyptians  constructed  paved  roads  for  their  use  in  build-  \ 
ing  the  Pyramids  as  long  ago  as  6000  B.  C.  The  Carthagenians  built 
a  system  of  military  roads  which  very  nearly  caused  the  downfall  of 
Rome.  The  Romans,  having  learned  their  lesson,  built  a  remarkable 
system  of  paved  highways  reaching  all  parts  of  their  Empire  and 
some  of  their  pavements  stand  today  as  a  monument  to  their  thorough- 
ness of  construction.  The  Roman  roads  were  the  most  substantial 
structures  of  the  kind  ever  laid  and  were  practically  solid  masonry 
three  or  four  feet  thick.  The  surface  consisted  of  large  flat  blocks 
of  stone  imbedded  in  mortar.  The  Appian  Way  built  about  300  B.  C. 
is  said  to  have  been  in  condition  for  travel  800  years  after  it's  con- 
struction, but  the  difference  in  the  character  and  amount  of  traffic 
must  be  considered  in  comparing  this  with  any  modern  construction. 
The  streets  of  ancient  Rome,  Pompeii,  Jerusalem,  Athens  and  other 
cities  were  paved.  In  fact  wherever  civilization  reached  a  high  state; 
of  development  in  ancient  times,  we  find  paved  streets  and  roads. 

In  modern  times,  however,  it  was  not  until  the  16th  Century 
that  any  attempt  was  made  to  improve  the  roads  of  France  or  Eng- 
land. Paris  had  a  population  of  probably  200,000  before  its  first 
pavements  were  built  in  1184.  The  first  regular  pavement  was  laid 
in  London  about  1533,  but  square  Granite  Blocks  were  not  introduced 
until  as  late  as  1760.  The  surfacing  of  the  streets  in  European 
cities  in  early  times  however  should  hardly  be  dignified  by  the  name 
of  pavement;  being  nothing  more  than  field  stones  tamped  into  the 
mud.  Even  with  the  light  traffic  of  those  days,  their  construction  and 
drainage  were  so  poor  that  their  condition  soon  became  detestable. 
It  is  related  that  the  coachmen  of  the  nobles  took  great  delight  in 
driving  into  the  holes  even  at  the  risk  of  upsetting  the  carriage  in 
order  to  witness  the  discomfiture  of  the  unwary  pedestrian  who 


10 


BRICK  PAVEMENTS 


was  splashed  from  head  to  foot  with  filthy  mud.  Late  in  the  18th 
Century  systematic  and  scientific  construction  of  pavements  began 
and  we  have  such  names  as  Tresaguet,  a  French  Engineer,  and  Tel- 
ford  and  Macadam,  Englishmen,  whose  influence  on  road  construe-, 
tion  has  been  felt  down  to  the  present  time.  Not  only  was  the  initial 
cost  lessened  and  a  better  surface  obtained  by  these  engineers,  but 
the  maintenance  cost  was  very  much  reduced.  Brick,  Stone  Block, 


Fig.  1 — A  Vertical  Fiber  Brick  Highway  in  Calcasieu  Parish,  Louisiana. 

and  Wood  pavements  came  into  use  at  about  the  same  time  with  the 
awakening  of  the  civic  consciousness  of  the  cities. 

Having  realized  the  necessity  of  less  haphazard  and  more 
careful  construction,  the  development  of  road  and  street  pavement 
progressed  fairly  rapidly,  although  it  was  not  until  1872  that  the  first 
concrete  base  for  paving  was  laid  in  London. 

In  the  United  States  street  surfacing  followed  much  the  same 
course  as  in  England.  Although  the  first  pavement  of  cobble-stone 
was  laid  in  New  York  in  1656,  it  was  almost  the  only  kind  used  until 


BRICK  PAVEMENTS  11 

1849,  while  the  concrete  base  was  not  introduced  until  as  late  as 
1880.  The  highways  of  the  United  States  were  not  improved  at  the 
same  rate  and  are  at  present  but  incompletely  and  poorly  developed. 
This  has  been  due  mainly  to  the  sparse  settlement  of  the  country 
and  to  the  excellence  of  the  railway  systems,  but  nearly  as  much 
blame  can  be  laid  to  our  system  of  administration,  which  has  been 
indifferent  and  has  not  given  the  proper  support  to  the  skillful  road 
engineer. 

The  public  lack  appreciation  of  the  benefits  derived  from  paved 
roads  and  are  still  inclined  to  believe  that  all  material  is  alike  or  that 
anyone  can  build  a  road.  The  main  roads  should  be  planned  and 
carried  out  as  a  national  policy  instead  of  being  left  to  the  various 
States,  Counties  or  Townships,  which  are  manifestly  incapable  of 
developing  a  co-ordinated  national  road  system. 

A  list  of  the  various  materials  experimented  with  for  paving 
surfaces  apparently  includes  everything  that  could  conceivably  be 
used  for  this  purpose.  The  materials  have  also  been  laid  in  all 
manner  of  ways  and  combinations.  An  iron  pavement  was  laid  in 
New  York  of  block  form  roughened  on  the  surface.  It  was  so  noisy 
and  caused  so  much  damage  to  horses,  which  tore  off  their  shoes, 
slipped  and  fell  frequently,  that  it  was  taken  up  after  a  short  trial. 
Various  forms  of  Iron  and  Concrete,  Iron  Ore,  Artificial  Stone  Blocks, 
divitrified  Glass,  compressed  Marsh  Grass,  or  Wood  Pulp,  by-pro- 
ducts of  sugar  refineries  and  so  on,  have  all  been  experimented  with, 
while  the  combinations  that  have  been  tried  with  wood  and  with 
asphalt  are  almost  without  number.  All  of  these  experiment's  can- 
not be  called  failures,  but  nearly  all  have  proven  impractical  for  one 
reason  or  another,  and  have  never  been  used  except  for  short 
stretches.  It  is  interesting  to  note  that  the  paving  materials  being 
used  now  are  the  ones  in  use  in  the  early  days  of  the  paving  in- 
dustry and  that  the  pavements  which  are  with-standing  modern  traf- 
fic and  modern  street  and  road  conditions  today  are  direct  descendents 
of  the  pavements  of  forty  years  ago.  A  gradual  improvement  in 
methods  of  manufacturing  and  laying,  as  machinery  and  a  better 
understanding  cf  the  material  developed,  has  taken  place  and  can  be 
traced  step  by  step  down  to  the  present.  Even  with  the  standard 
materials,  there  have  been  many  failures  of  pavements,  mainly  due 
to  a  lack  of  appreciation  of  the  characteristics  of  the  material  used  or 
a  disregard  of  accepted  Engineering  design.  Generally  speaking, 
however,  constant  progress  has  been  made  and  the  pavements  of 
today  are  as  a  rule  many  times  better  than  those  of  forty  or  even 
twenty  years  ago. 

In  no  case  has  this  progressive  improvement  been  more  mark- 
ed or  taken  along  surer  lines  than  in  brick  paving.  Brick  pave- 
ments have  been  used  in  the  Netherlands  for  nearly  two  centuries, 
and  some  of  them  which  are  over  fifty  years  old  are  still  in  fair 
condition.  Byrne  says  the  old  brick  pavements  in  the  Hague,  Hol- 
land, are  laid  of  hard  burned  brick  about  Sy2  inches  long,  4*4 
inches  wide  and  2%  inches  deep  and  are  laid  with  the  joints  as 
close  as  possible.  Amsterdam  is  paved  almost  entirely  with  brick 
as  are  also  a  number  of  roads  throughout  the  country.  The  com- 
mercial city  and  seaport  Rotterdam,  with  its  warehouse  and  dock 


BRICK  PAVEMENTS  13 

traffic,  has  used  brick  successfully  for  many  years.  The  early  pave- 
ments were  laid  on  sand,  but  later  a  hydraulic-cement  was  used  with 
the  sand  to  form  the  base  and  the  bricks  laid  on  this.  This  was 
before  the  time  of  concrete  bases.  Brick  pavement  has  also  been 
used  in  Japan  since  very  ancient  times,  but  was  very  crudely  built. 
Other  countries  have  used  brick  to  more  or  less  extent,  but  in  the 
United  States  it  has  reached  its  greatest  perfection. 

It  was  not  until  about  1870  that  the  first  brick  pavement  was 
laid  in  the  United  States  at  Charleston,  West  Virginia.  It  is  said 
that  this  pavement  was  laid  by  a  private  citizen  at  his  own  expense 
in  spite  of  the  ridicule  of  his  neighbors.  Two  or  three  years  later, 
the  city  laid  a  stretch  of  brick  pavement  which  was  in  good  con- 
dition in  1900  and  had  received  very  little  repairs. 

Bloomington,  Illinois,  laid  its  first  brick  pavement  in  1875,  and 
a  great  many  small  cities  throughout  the  central  west  began  the 
use  of  brick  in  the  80's.  The  first  large  city  to  lay  brick  pavement 
was  Philadelphia  in  1887  and  it  has  laid  a  continually  increasing 
amount  on  account  of  its  popularity  until  there  is  at  present  a  very 
large  mileage  of  brick  in  use  there. 

Cleveland,  Ohio,  began  laying  brick  in  1889  and  in  1913  had 
over  328  miles  of  brick  streets.  A  large  majority  of  the  pavement 
in  Cleveland  was  laid  on  a  sand  foundation,  and  on  this  account 
some  of  it  has  required  relaying  in  less  than  15  years,  although  much 
of  it  over  20  years  old  is  still  in  use. 

The  first  brick  pavement  in  Chicago,  Illinois,  was  laid  on  Lake 
Avenue  from  35th  Street  to  37th  Street  in  1893,  and  was  still  in  use 
after  seventeen  years  of  heavy  traffic,  although  badly  worn.  This 
was  a  two  course  brick  pavement. 

Kansas  City,  Missouri,  began  using  brick  for  paving  about 
1890  and  has  over  850,000  square  yards  of  it  in  use  at  present  on 
streets  alone.  Of  this  total  over  493,000  square  yards  is  over  ten 
years  old,  of  which  439,000  square  yards  has  seen  fifteen  years  or 
more  of  service.  There  were  over  132,400  square  yards  in  use  in 
1916,  which  had  been  down  and  in  use  20  years  or  more.  The 
oldest  brick  pavements  in  Kansas  City  are  25  years  old.  These  brick 
paved  streets  which  have  seen  ten  years  or  more  service  include 
wholesale  and  retail  business,  street  car  line  streets  and  residence 
streets  scattered  throughout  the  older,  built-up  part  of  the  city. 
In  fact  some  of  the  oldest  brick  pavements  are  on  streets  in  or 
near  the  business  section  and  have  always  received  a  very  con- 
siderable amount  of  traffic.  Less  than  30%  of  these  streets  have 
ever  received  any  repairs  due  to  wear  and  these  repairs  have  generally 
been  of  an  inexpensive  and  minor  character.  Thirteenth  Street 
from  Oak  to  Woodland,  which  is  close  to  the  business  section  of  the 
City,  receives  considerable  traffic  and  was  laid  in  1894.  The  joints 
were  filled  with  sand  and  the  bricks  are  consequently  rounded  on 
top.  There  are  some  places  at  the  intersections  which  need  repairs, 
but  the  pavement  as  a  whole  is  in  good  condition  and  will  probably 
give  a  number  of  additional  years  service.  Tenth  Street  from  Central 
to  Wyandotte  was  paved  with  brick  in  1892,  and  has  been  repaired 
once  by  raising  some  sunken  places  and  turning  the  brick.  It  was 
in  fair  condition  in  1916.  No  other  kind  of  pavement  in  Kansas  City 
can  show  as  long  life  or  as  low  maintenance  cost  as  brick.  The 
brick  pavements  laid  in  recent  years  are  giving  good  satisfaction  and 


BRICK  PAVEMENTS  15 

from  present  indications  should  beat  the  records  of  their  predeces- 
sors. 

Where  the  use  of  brick  has  been  once  commenced  in  the  im- 
provement of  country  roads,  the  community  has  been  so  well  satis- 
fied that  it  has  been  adopted  for  the  main  traveled  roads  and  is  often 
the  only  material  used  in  some  towns. 

To  take  two  examples:  Cuyahoga  County,  Ohio,  had  over 
400  miles  of  brick  roads  in  1913,  and  King  County,  Washington, 
recently  laid  over  18  miles  of  brick  on  the  mountainous  roads  out- 
side of  Seattle. 

When  the  inadequate  foundations,  the  quality  of  the  brick 
and  the  method  of  laying  are  all  considered,  it  is  somewhat  sur- 
prising that  the  earlier  brick  pavements  have  been  so  successful  and 
have  had  such  an  exceptionally  long  life.  It  has  awakened  the  brick 
manufacturers  and  highway  engineers  to  the  possibilities  of  this 
material  to  such  an  extent  that  the  value  of  paving  brick  manu- 
factured in  the  United  States  has  rapidly  increased  until  it  now 
represents  one  of  the  important  industries.  At  first  there  was  little 
discrimination  in  the  kind  of  brick  used  and  even  the  best  quality 
brick  laid  in  the  early  days  would  not  now  be  considered  suitable  for 
paving.  To  most  people  at  that  time  and  to  some  even  now  a 
brick  was  a  brick  without  regard  to  its  manufacture.  Few  or  no 
tests  were  required  to  determine  the  suitableness  or  wearing  quali- 
ties of  the  various  brands  of  brick,  with  the  result  that  some  poor 
pavement  was  laid. 

Inexperience  in  designing  and  laying  is  also  responsible  for 
many  of  the  defects  in  the  older  brick  pavements.  It  is  unfortunate- 
ly an  easy  matter  in  this  country  to  cite  numerous  examples  of 
failure  or  defects  in  any  kind  of  paving  material.  This  is  an  in- 
dictment against  the  American  method  of  hasty,  careless,  temporary 
construction  as  opposed  to  the  thoroughness,  thoughtfulness  and 
permanence  demanded  by  good  paving.  Invariably  where  reported 
failures  in  brick  pavement  have  been  investigated,  it  has  been  found 
that  poor  material,  poor  design  or  poor  workmanship  is  responsible, 
all  of  which  could  have  been  avoided.  If  public  officials  could  be 
made  to  see  the  ultimate  economy  in  the  employment  of  a  capable, 
experienced  highway  engineer  and  would  use  some  care  and  deter- 
mination in  the  selection  of  the  manufacturer  who  furnishes  the  ma- 
terial and  the  contractor  who  constructs  the  pavement,  even  if  the 
first  cost  is  a  little  more,  then  years  would  be  added  to  the  life  of 
our  pavements  and  the  public  will  have  increased  satisfaction  in 
their  use. 

Brick  paving  has  been  developed  to  a  high  state  of  perfection. 
The  method  of  manufacture  and  of  laying  has  been  standardized 
to  a  great  extent,  and  with  experienced  and  conscientious  inspection, 
its  satisfaction  and  behavior  can  be  foretold  with  a  great  degree  of 
certainty.  The  brick  material  may  be  had  in  small  units  of  prac- 
tically uniform  size,  in  large  or  small  quantities,  and  of  uniform 
quality.  It  is  nearly  non-absorbent,  has  more  than  sufficient  strength 
to  with-stand  the  heaviest  wheel  and  toe-calk  loads  of  modern  traffic 
and  is  unaffected  by  water,  frost,  weathering  or  age.  Vitrified  clay 
is  more  permanent  than  some  granites  in  this  last  named  respect. 


16  BRICK  PAVEMENTS 

Brick  pavement  offers  as  low  tractive  resistance  at  all  sea- 
sons of  the  year  as  any  paving  material.  If  one  horse  can  just  draw 
a  given  load  along  a  level  brick  road,  it  will  take  l1^  to  1%  horses 
to  draw  the  same  load  on  a  sheet  asphalt  surface,  depending  on  the 
season  of  the  year;  2  horses  for  granite  block,  3  horses  on  macadam, 


Sandy  Road  Good  Earth  Macadam 


5  horses  to  draw  the  same  load  on  a  good  earth  road,  20  horses 
on  a  sandy  road  or  30  horses  through  deep  sand,  all  of  the  pave- 
ments to  be  assumed  dry  and  in  good  condition.  This  illustrates 
better  than  anything  else  the  part  that  tractive  resistance  plays. 
The  computation  is  based  on  a  large  number  of  experiments  per- 
formed by  the  United  States  Government,  and  by  private  investiga- 
tors, both  here  and  abroad. 

Although  'brick  pavement  has  a  pleasing  smoothness,  it  af- 
fords a  good  foothold  for  horses  and  possesses  adequate  frictional 
properties  for  rubber  tired  vehicles  regardless  of  weather  con- 
ditions. Brick  can  therefore  be  used,  when  proper  methods  of  con- 
struction are  employed,  on  all  grades  with  safety.  It.  does  not  wear 
slippery  but  increases  in  serviceability  with  age. 

Brick  pavement  can  also  be  laid  at  a  reasonable  first  cost,  and 
on  account  of  its  durability  and  low  maintenance  cost,  it  has  a  very 
low  cost  per  year  distributed  over  a  term  of  years.  Pavements  should 
be  treated  as  an  investment  and  so  designed  and  constructed  that 
each  dollar  of  investment  will  return  the  greatest  amount  of  service. 

Even  with  the  early  brick  surfaces  the  life  has  averaged  over 
fifteen  years  and  with  modern  construction  it  will  undoubtedly  be 
much  greater.  Public  officials  are  possessed  with  the  laudable  de- 
sire to  make  as  big  a  showing  with  the  money  at  their  command  as 
possible,  but  this  should  not  be  carried  to  such  an  extent  as  to  lose 
sight  of  the  principles  of  suitableness  or  serviceability.  They  do  not 
do  this  in  their  own  affairs  and  should  therefore  invest  public  money 
in  such  a  way  as  to  get  the  greatest  return.  Brick  paving  has  a 
well  deserved  reputation  for  the  lowest  annual  repair  cost  of  any 
pavement,  except  granite  block.  Brick  pavement  may  be  expeditious- 
ly  laid,  requires  no  expensive  contractors  outfit  or  especially  expert 
labor,  so  that  the  fullest  competition  in  letting  the  contract  may  be 
obtained. 

It  is  a  comparatively  easy  matter  to  repair  service  cuts  which 
may  be  necessary  after  the  pavement  is  laid,  and  should  defects  in 
the  surface  occur,  the  repairs  are  easily  and  quickly  made  with  a 
small  force  and  no  special  equipment.  This  is  of  importance  to  those 
in  charge  of  country  roads  or  street's  in  towns  or  small  cities. 


BRICK  PAVEMENTS  17 

Pavements  which  require  expensive  plant  equipment  for  laying  or 
technical  specialists  to  see  that  the  specifications  are  being  complied 
with,  place  the  authorities  at  a  disadvantage  and  may  also  prevent 
the  fullest  competition  among  paving  contractors.  It  soon  becomes 
a  serious  proposition  to  properly  maintain  such  pavements  without 


Granite  Block  Sheet  Asphalt  Brick 


engaging  a  chemist  and  investing  in  proper  and  expensive  equipment. 

Brick  pavement  is  unaffected  by  weathering,  by  water  or  by 
mud  on  the  surface  and  does  not  itself  produce  mud  or  dust.  It  is 
easily  cleaned  either  by  flushing,  sweeping  or  machine  brooms.  It 
also  has  a  clean,  fresh  appearance  and  being  non-absorbent  it  is 
also  sanitary. 

When  properly  laid  it  is  not  noisy,  gives  an  excellent  riding 
surface  for  all  classes  of  vehicles,  and  presents  a  pleasing  appear- 
ance. 

With  recent  developments  in  brick  manufacture  and  methods 
of  laying,  brick  pavement  can  be  designed  to  economically  take  care 
of  the  light  traffic  of  a  country  road  or  the  heaviest  traffic  of  a  city 
street,  to  give  a  sanitary,  quiet,  easy  riding  surface  for  a  residence 
street,  or  a  cheap,  dustless,  durable,  low  maintenance  pavement  for 
the  business  section.  It  is  no  longer  necessary  to  use  the  same 
depth  of  brick  surfacing  or  lay  it  the  same  on  a  country  road  as 
around  a  city  warehouse.  Engineers  should  familiarize  themselves 
with  these  improvements  and  use  the  type  of  construction  economi- 
cally suitable  and  possessing  the  qualities  which  it  is  desirable  to 
emphasize,  depending  on  the  use  of  the  street  to  be  paved.  The 
various  types  of  brick  pavement  and  their  characteristics  will  be 
discussed  in  later  chapters. 

Brick  pavement  has  established  itself  as  a  standard  pave- 
ment of  the  highest  quality  through  a  long  period  of  exceptional 
durability  and  service  in  all  parts  of  the  country.  It  can  be  de- 
signed to  take  care  of  all  conditions  of  modern  traffic  at  a  reasonable 
first  cost  with  a  very  low  yearly  maintenance  cost.  It  can  be  laid 
and  repaired  without  large  plant  equipment.  It  does  not  deteriorate 
with  age  and  is  not  noisy.  While  possessing  a  pleasing  appearance 
and  an  easy  riding  smoothness,  it  affords  a  good  foothold  for  horses 
and  all  classes  of  vehicles  and  is  capable  of  withstanding  the  shock 
and  abrasion  of  the  heaviest  traffic. 

Brick  pavement  offers  a  low  tractive  resistance  and  is  especial- 
ly favorable  to  all  classes  of  traffic;  being  non-absorbent,  non-dust 
or  mud  producing,  and  easily  and  effectively  cleaned,  it  is  sanitary. 
A  properly  constructed  brick  pavement  is  an  ideal  pavement  in  all 
respect's. 


CHAPTER  II 

HIGHWAY   ECONOMICS 

HE  TERM,  HIGHWAY,  is  used  to  designate  any  public  thorough- 
fare or  line  of  communication  whether  in  the  country, 
town  or  city — whether  a  road,  a  boulevard,  a  street  or  an  alley. 
The  highway  takes  account  of  the  entire  width  of  the  street 
"or  road,  including  sidewalks  and  the  tree  planting  space,  while 
carriageway  or  roadway  refers  more  specifically  to  the  paved  or 
traveled  portion  of  the  highway.  Economics  is  the  science  of  the 
careful,  judicious  use  or  management  of  a  thing.  In  studying  the 
science  of  the  judicious  use  of  public  thoroughfares,  the  question 
naturally  rises  as  to  what  returns  may  be  expected  from  improved 
roads  and  streets.  Do  the  advantages  gained  by  paved  roadways 
warrant  the  expenditure  of  the  money  necessary  for  their  proper 
construction?  Recognizing  that  certain  circumstances  may  alter 
cases,  all  students  of  highway  economics  agree  that  in  the  large 
majority  of  cases  in  the  United  States,  improvement  of  roads  is  worth 
much  more  than  the  cost. 

There  is  no  record  that  any  community  has  ever  regretted  the 
improvement  of  its  public  thoroughfares  and  it  invariably  happens 
that  once  started,  construction  work  is  carried  on  as  fast  as  finances 
will  permit.  It  is  like  the  claim  made  for  a  certain  confection,  the 
more  improved  highways  a  community  has,  the  more  it  finds  it  needs 
and  wants.  This  is  the  history  of  street  and  road  improvement  in 
every  locality. 

The  advantages  to  be  gained  through  paved  roads  by  the  farm- 
ers and  by  the  residents  of  small  towns  are  in  many  ways  so  obvious 
that  it  seems  scarcely  necessary  to  call  attention  to  any  but  the  most 
important  cases. 

An  improved  road  reduces  the  cost  of  hauling  very  material- 
ly. This  reduction  does  not  always  appeal  to  the  farmer  who  does  his 
own  teaming,  because  his  cost  is  indirect  and  is  paid  for  by  the 
time  and  labor  of  himself  and  his  horses.  It  is  sometimes  brought 
home  to  him  forcibly,  however,  when  he  meets  a  friend  in  town 
who  lives  on  a  hard  surfaced  road  and  has  from  three  to  ten  times 
the  load  behind  his  team  that  he  himself  has  been  able  to  haul  over 
a  dirt  road.  Considering  the  time  of  a  farmer  and  his  team  as 
worth  something,  estimates  have  been  made  of  the  cost  of  hauling 
farm  produce  which  run  into  the  hundreds  of  million  dollars.  It  is 
impossible,  however,  to  determine  with  any  degree  of  accuracy  the 
saving  in  cost  of  hauling  effected  by  paved  roads.  That  hard  surfaced 
roads  do  reduce  the  cost  is  evidenced  by  the  fact  that  farm  land 
served  by  them  commands  a  higher  price  than  just  as  good  land  the 
same  distance  from  the  market,  but  on  a  dirt  road.  At  average  prices 
for  labor  and  teams  and  with  full  loads  on  level  roads  the  cost  of 
hauling  one  ton,  one  mile  may  run  over  60  cents  on  dry  sand,  40 
cents  on  a  fairly  good  but  muddy  road,  to  as  low  as  10  or  12  cents 
on  an  earth  road  in  dry,  good  condition;  while  on  a  level  brick  pave- 
ment the  cost  varies  from  2  to  5  cents  per  ton  mile,  depending  on 
its  condition.  On  this  basis  an  enormous  saving  is  obtained  by  paved 


20 


HIGHWAY  ECONOMICS 


roadways.  This  may  be  compared  with  railroad  transportation  which 
is  carried  on  at  a  cost  of  about  %  cent  per  ton  mile.  It  is  also  well 
to  compare  the  attention  given  to  railways  in  order  to  reduce  their 
cost  of  transportation  with  the  amount  of  maintenance  given  the 
average  road. 

Practically  all  merchandise  and  produce  must  at  one  time  or 
another  in  its  journey  from  producer  to  consumer  be  hauled  over 
highways,  some  of  it  several  times.  The  wheat  must  be  hauled  to 


Fig.   5 — A  Vitrified  Brick  Road,   St.   Louis   County,   Missouri. 

the  railroad  or  mill  and  the  flour  is  usually  delivered  over  pavements 
to  the  consumer.  The  cotton  may  make  several  trips  over  roads  on 
its  way  from  plantation  to  the  shirt  on  your  back.  The  highways  of 
the  country  are  the  feeders  and  the  ultimate  distributors  for  the  rail- 
roads. While  we  are  astounded  at  the  magnitude  of  the  freight  ton- 
nage hauled  by  the  railroads,  we  fail  to  realize  the  equally  enormous 
traffic  of  our  city  and  country  highways.  This  traffic  is  widely  dis- 
tributed, is  in  small  units,  and  the  amount  done  by  any  one  individual 
is  only  a  minute  part  of  the  total.  The  small  economic  gain  of  the  in- 
dividual, however,  makes  the  economic  prosperity  of  the  community, 


HIGHWAY  ECONOMICS  21 

and  the  community  which  reduces  the  cost  and  facilitates  the  collec- 
tion of  those  things  it  has  to  sell  and  the  distribution  of  those  things 
it  must  buy  is  bound  to  forge  ahead.  While  railway  corporations  are 
watching  the  hundredth  of  a  cent  variation  in  their  ton  mile  cost  of 
transportation,  are  we  not  overlooking  a  great  opportunity  in  failing 
to  improve  our  roads  and  streets  with  easy  grades  and  durable  pave- 
ments, and  so  reduce  the  cost  of  transportation  over  them  from  five 
to  ten  times? 

The  most  tangible  benefit  of  a  hard  surfaced  road  to  the  agri- 
culturist is  that,  if  it  is  constructed  of  proper  materials,  it  is  service- 
able the  year  around,  in  all  seasons  and  under  all  conditions  of 
weather.  The  road  is  always  ready  to  transport  the  maximum  load. 
This  fact  is  of  great  advantage  to  the  farmer,  both  as  a  matter  of 
convenience  and  for  financial  reasons.  He  immediately  has  the  power 
to  market  his  crops  under  the  most  favorable  market  conditions 
and  is  not  obliged  to  sell  them  during  the  most  favorable  local 
weather  condition.  He  has  a  wider  choice  of  the  time  of  marketing 
and  by  taking  advantage  of  favorable  price  conditions,  he  may  often 
realize  a  considerable  additional  profit  on  his  produce.  His  mar- 
ket radius  is  also  enlarged.  If  the  nearest  buyer  offers  less  than 
one  a  little  further  away,  he  can  afford  to  make  the  additional 
haul  over  the  paved  road  in  order  to  avail  himself  of  the  better  price. 
This  argument  of  course,  applies  with  equal  force  to  the  purchase 
of  supplies  by  the  farmer.  Owing  to  the  greater  speed  and  ease 
of  traveling,  he  can  take  advantage  of  the  competition  among  mer- 
chants, and  without  regard  to  weather  conditions,  often  when  work 
on  the  farm  is  tied  up  because  of  bad  weather,  he  can  sell  where 
the  highest  prices  prevail  and  buy  where  values  are  the  cheapest. 

The  365-day  road  also  enables  the  land  owner  to  cultivate  crops 
otherwise  not  marketable.  The  dairy  and  poultry  products,  fruit  and 
fresh  vegetables,  require  marketing  when  they  are  mature  in  order  to 
realize  the  best  prices.  Even  if  there  are  not  many  days  when  the  dirt 
road  is  absolutely  impassable,  these  days  may  occur  at  a  time  when  a 
crop  of  perishable  produce  is  ripe  and  cause  a  total  loss.  Some 
farm  produce  requires  daily  marketing  and  a  farm  on  a  dirt  road 
cannot  undertake  to  raise  this  class  of  produce  profitably  unless  very 
close  to  the  market. 

Where  all  season  roads  have  been  constructed  near  our  cities 
daily  hauls  by  auto  truck  of  from  25  to  50  miles  are  not  at  all  un- 
common, so  that  the  outlying  farmer  may  market  his  fresh  vegetables 
and  dairy  products  to  advantage.  In  fact  transportation  by  automo- 
bile, of  which  so  much  in  the  way  of  market  radius  and  saving  in  cost 
and  time  is  being  accomplished,  depends  primarily  for  its  success  on 
smooth,  durable,  paved  roadways. 

These  advantages  accrue  in  other  ways  to  the  towns  and 
cities  served  by  paved  roads.  By  making  travel  easier  and  indepen- 
dent of  the  season  of  the  year,  they  materially  widen  the  radius  of 
the  commercial  town  and  equalize  the  mercantile  business  from  week 
to  week.  The  land  owners,  being  more  prosperous,  are  induced  to 
come  to  town  more  frequently  and  buy  more  liberally. 


22  HIGHWAY  ECONOMICS 

Good  roads  also  induce  tourist  travel  and  vacation  residents 
who  are  a  source  of  legitimate  profit  to  the  community.  Switzerland 
is  maintained  almost  entirely  by  the  revenue  derived  from  tourists. 
The  rapid  increase  in  automobile  tourist  travel  is  due  to  the  in- 
creased mileage  of  paved  roads  and  while  the  automobilist  clamors 
for  more  and  takes  pleasure  out  of  those  already  built,  the  real  fin- 
ancial benefit  comes  to  the  community  which  encourages  his  visits. 


Fig-.  6— A  Vitrified  Brick  Road  Near  Wichita,  Kansas. 

The   pleasure   tourist  usually   spends   considerable  money  and  takes 
nothing  away  with  him. 

With  the  automobile,  such  a  factor  in  quick,  convenient  trans- 
portation over  hard  surfaced  roads,  rural  land  for  some  distance  from 
towns  and  cities  becomes  suburban  land  for  workers  in  the  City  who 
enjoy  and  can  afford  the  country  life,  making  a  consequent  increase 
in  the  value  of  land.  Good  roads  by  making  land  more  available  at 
all  seasons  of  the  year,  increase  the  possible  number  of  buyers,  and 
the  land  owner  receives  a  better  price  if  he  sells.  Or  on  a  forced 
sale  the  land  will  bring  more  nearly  what  it  is  worth  as  it  has  a 
better  market. 


HIGHWAY  ECONOMICS  23 

An  intangible  advantage  of  all-season  paved  roads  and  yet  a 
very  real  one,  is  the  promotion  of  social  intercourse  between  both 
the  landholders  themselves,  and  between  the  residents  of  the  towns 
and  the  farmers.  The  privilege  or  opportunity  of  visiting  ones  neigh- 
bors, or  attending  social  gatherings,  lectures,  churches,  or  theatres, 
with  ease  and  comfort,  adds  much  to  the  pleasures  of  country  life. 
With  the  extension  of  the  rural  free  mail  and  parcel  post  delivery 
and  the  increased  use  of  the  automobile  for  getting  about,  the  success 
of  both  of  which  depends  on  having  365-day  roads,  life  in  the  country 
has  been  much  enriched  and  benefited.  The  self-respect  of  the  farm- 
ers has  been  stimulated  and  broken  down  fences  have  been  repaired, 
shrubs  trimmed,  and  the  general  comfort  and  appearance  of  the  farm 
house  improved.  With  paved  roads  it  has  been  possible  to  consoli- 
date the  rural  schools,  so  that  more  competent  teachers  can  be 
employed  and  more  extended  and  broader  education  offered  to  the  chil- 
dren. In  many  places  these  rural  school  houses  have  become  the 
social  centers  for  a  large  number  of  families  and  are  used  to  the  help 
and  pleasure  of  the  older  as  well  as  the  younger  members. 

All  of  these  advantages — what  may  be  termed  the  durable  satis- 
factions of  life;  the  things  that  make  life  worth  living,  can  only  be 
successfully  enjoyed  to  their  full  extent  by  sections  which  have 
smooth,  well  constructed  paved  roads,  ready  for  use  every  day  in 
the  year. 

The  advantages  of  paved  roads  may  therefore  be  sumed  up  in 
two  classes;  as  the  tangible,  money-saving  benefits,  due;  (1)  to  the 
reduced  cost  of  hauling;  (2)  to  being  able  to  market  crops  at  the 
most  favorable  prices;  (3)  to  a  wider  choice  of  market;  (4)  to  a 
wider  choice  of  the  time  of  marketing;  (5)  to  being  able  to  cultivate 
more  diversified  crops;  (6)  to  making  possible  the  use  of  auto-trans- 
portation; (7)  to  a  wider  radius  of  the  commercial  town;  (8)  to  equal- 
izing the  mercantile  business  of  the  town  merchants;  (9)  to  the  en- 
couragement of  tourist  travel;  (10)  to  the  changing  of  rural  land  to 
suburban  property;  (11)  to  a  wider  market  for  the  land  itself  and  its 
greater  salable  value;  and  the  intangible  benefits  due:  (1)  to  the  much 
improved  facility  for  social  intercourse;  (2)  to  the  rural  mail  delivery 
extension;  (8)  to  the  consolidation  of  rural  schools;  (4)  to  the  pleasure 
and  recreation  in  driving;  (5)  to  the  mental  stimulation  of  the  people 
living  on  an  improved  highway.  If  these  benefits  are  not  forthcoming 
it  is  because  the  people  have  not  made  the  fullest  use  of  a  properly 
constructed  road. 

The  value  of  an  economical,  durable,  pavement  on  the  streets  of 
our  towns  and  cities  is  somewhat  similar  to  the  country  road  since 
paved  streets  promote  the  social,  financial,  and  educational  well-being 
of  the  residents.  Paved  streets  reduce  the  cost  of  transportation  and 
establish  a  permanent  grade  for  the  further  development  of  the  street 
and  the  buildings  on  the  adjoining  property.  Numerous  paved  streets 
in  a  town  increase  the  facilities  for  fire  protection.  The  proportion 
of  miles  of  pavement  to  the  miles  of  all  streets  is  one  of  the  things 
always  reported  by  the  fire  insurance  rate  adjusters.  Pavements  ma- 
terially improve  the  appearance  and  beauty  of  business  as  well  as 
residence  streets.  A  well  drained,  impervious,  smooth,  dustless 
pavement,  adds  to  the  cleanliness  of  the  homes  of  the  residents  along 
the  street,  and  by  the  elimination  of  mud  and  stagnant  pools  in  wet 
weather,  and  dust  in  dry  weather,  the  street  ceases  to  be  a  breeder 


24 


HIGHWAY  ECONOMICS 


for  disease  germs  and  for  mosquitoes  and  flies  which  carry  disease. 
A  paved  street  is  a  sanitary  measure  of  fundamental  importance. 
The  paving  of  the  streets  of  the  cities  of  Cuba  and  Panama  was  one 
of  the  things  first  demanded  by  the  American  sanitary  experts  in  their 


Fig.    7 — An   Unpaved    Street   is    Frequently    a    Sorry    Sight. 

fight  against  squalor,  filth,  and  fever.  It  is  interesting  to  note  in 
passing  that  brick  shipped  from  the  United  'States  was  the  paving 
material  selected  for  Panama,  although  other  paving  materials  nearer 
at  hand  were  cheaper. 


HIGHWAY  ECONOMICS  25 

Well  paved  streets  promote  social  intercourse  and  pleasure 
driving;  a  most  delightful  form  of  recreation.  It  is  a  well  known 
fact  that  paving  increases  the  value  of  abutting  property  to  a  greater 
amount  than  the  cost  of  the  paving  itself.  This  is  recognized  by  real 
estate  dealers,  who  invariably  pave  the  streets  of  their  additions,  if 
they  can  obtain  the  capital  necessary,  before  placing  the  property  on 
the  market.  Loans  on  property  facing  a  well  paved  street  can  usually 
be  obtained  at  a  lower  rate  of  interest  than  equally  as  good  property 
on  an  unpaved  street.  This  is  because  investors  realize  that  property 
on  a  paved  street  can  be  more  easily  disposed  of  and  to  better  ad- 
vantage on  a  quick  sale.  It  is  more  desirable  and  commands  the  at- 
tention of  a  large  number  of  buyers.  Pavement  is  in  reality  an  in- 
vestment in  the  improvement  of  the  abutting  property  as  much  as 
any  building  erected  on  the  property  itself,  and  like  the  building,  if 
constructed  of  proper  materials  and  in  a  proper  manner,  it  will  re- 
turn good  interest  on  the  investment.  Paved  city  streets,  therefore 
bring  the  following  benefits: 

1.  A  lowered  cost  of  transportation. 

2.  The  establishment  of  a  permanent  grade. 

3.  Sanitary  and  healthful  street  conditions. 

4.  Cleaner  homes  and  places  of  business. 

5.  Greater  comfort  and  better  living  conditions. 

6.  Improvement  in   the  'beauty  and  appearance   of  both   resi- 
dence and  business  streets. 

7.  Increased  facility  for  social  intercourse  and  pleasure  driv- 
ing. 

8.  Increased  fire  protection  with  consequent  lower  insurance 
rates. 

9.  Increase  in  the  value  of  the  abutting  land,  part  of  which  is 
a  measure  of  the  above  benefits. 

10.  Increased  desirability  of  the  abutting  property  with  lower 
rate  of  interest  on  loans  and .  a  greater  number  of  buyers  available 
for  quick  sale. 

It  is  important  to  keep  these  objects  and  benefits  of  paved 
roads  and  streets  in  mind  in  laying  out,  grading  and  constructing 
them,  so  that  the  fullest  realization  of  these  benefits  may  accrue  to 
the  community. 

The  proper  location,  grade,  and  wearing  surface  of  a  street  or 
road  are  the  most  important  factors  in  the  attainment  of  these  ad- 
vantages. The  location  and  grade,  however,  involve  so  many  things 
peculiar  to  a  given  locality  or  section  of  the  country,  that  only  a 
few  of  the  general  principles  regarding  safe  and  cheap  transportation 
can  be  given. 

The  force  necessary  to  haul  a  loaded  vehicle  is  consumed  (1) 
by  axle  friction,  (2)  by  air  resistance,  (3)  by  grade  resistance,  and  (4) 


26 


HIGHWAY  ECONOMICS 


by  rolling  resistance.  The  first  three  are  independent  of  the  road 
surface  and  depend  on  the  construction  of  the  vehicle,  the  speed  at 
which  it  travels  and  the  force  of  gravity.  The  rolling  resistance  de- 
pends somewhat  on  the  diameter  of  the  wheels  and  the  width  of  the 
tires,  but  more  especially  on  the  surface  supporting  the  vehicle.  It 


Fig-.  8 — A  Vitrified  Vertical  Fiber  Brick  Paved  Street  Has  an  Air  of 
Cleanliness    and    Respectability. 


is  the  greatest  factor  in  determining  the  power  required  to  move  a 
given  load  on  a  level  road.  The  United  States  Department  of  Agri- 
culture has  determined  that  a  horse  and  an  ordinary  wagon  will  haul 
the  following  loads  over  level  roads;  muddy  earth,  from  nothing  to 
800  pounds;  smooth  dry  earth,  1,000  to  2,000  pounds;  poor 
gravel  roads,  from  1,000  to  1;500  pounds;  good  gravel,  3,300 
pounds;  rock  or  macadam,  from  2,000  to  5,000  pounds,  and  brick, 


HIGHWAY  ECONOMICS  27 

from  5,000  to  8,000  pounds.  Since  all  factors  of  load  resist- 
ance were  the  same  in  these  experiments,  except  the  road  sur- 
face itself,  the  great  difference  in  tractive  resistance  of  various  sur- 
faces is  apparent.  It  has  been  determined  that  a  horse  can  exert  a 
pull  of  one-tenth  its  weight,  at  a  walk,  continuously  during  a  ten 
hour  work  day,  six  days  a  week,  and  the  maximum  pull  which  can 
be  exerted  is  about  one-half  of  its  weight  for  short  distances  only. 
On  grades  of  a  few  hundred  feet  it  may  be  assumed  that  a  horse  can 
exert  a  pull  of  one  quarter  of  its  weight.  Now  the  resistance  of  a  load 
on  an  incline  due  to  gravity,  that  is  the  grade  resistance,  can  be 
shown  to  be  approximately  20  pounds  per  ton  multiplied  by  the  per 
cent  of  grade.  By  exerting  a  pull  of  one-tenth  of  its  weight,  a  1,200 
pound  horse  can  haul  4  tons  on  a  level  brick  road  in  fair  condition; 
the  tractive  resistance  being  30  pounds  per  ton.  The  grade  resistance 
for  this  load  is  4  tons,  the  load,  plus  0.6  tons,  the  weight  of  the  horse 
multiplied  by  20,  or  92  pounds  for  each  per  cent  of  grade.  The  horse 
can  exert  a  pull  for  a  short  time  of  one-fourth  its  weight  or  300 
pounds,  of  which  120  pounds  is  used  to  overcome  tractive  resistance 
and  the  balance,  or  180  pounds,  is  used  to  overcome  grade  resistance 
at  the  rate  of  92  pounds  for  each  per  cent  or  a  maximum  allowable 
grade  of  about  2  per  cent.  On  a  dry,  packed  earth  road,  where  the 
tractive  resistance  is  100  pounds  per  ton  the  maximum  load  hauled 
on  the  level  is  reduced  to  1.2  tons  and  the  grade  resistance  for  this 
load,  including  the  weight  of  the  horse,  is  36  pounds  for  each  per  cent 
of  grade.  The  surplus  power  of  the  horse,  or  180  pounds,  will  there- 
fore haul  the  load  up  a  5  per  cent  grade  of  short  length.  These  ex- 
amples are  cited  to  show  the  great  importance  in  maintaining  a  low 
grade  on  improved  highways.  The  force  of  gravity  acts  alike  on 
loads  of  the  same  amount  independent  of  the  surface  they  are  hauled 
over,  and  it  is  therefore  a  greater  proportion  of  the  total  rolling 
resistance  the  less  the  tractive  resistance  or  the  better  the  road  surface 
and  the  greater  the  load.  A  horse  would  of  course  haul  a  greater  load 
up  a  5  per  cent  grade  paved  with  brick  than  up  the  same  grade  on 
an  earth  road,  but  in  order  to  take  the  fullest  advantage  of  the  low 
tractive  resistance  of  brick  pavement,  the  grades  should  be  so  low 
as  not  to  be  the  factor  limiting  the  loads. 

In  hilly  country  2%  grades  are  often  impractical.  The  maxi- 
mum grades  on  the  main  thoroughfares  should  not,  however,  exceed 
5%  or  possibly  6%  even  in  mountainous  country.  Every  effort  should 
be  made  by  economical  and  careful  engineering  to  reduce  this  maxi- 
mum to  as  low  a  point  as  possible,  and  especially  to  see  that  the 
maximum  grade  between  any  two  centers  of  population,  the  ruling 
grade  it  is  called,  is  not  much  greater  than  the  average  run  of  grades 
between  these  points.  The  maximum  or  ruling  grade  should  be  re- 
duced as  low  as  practical  and  all  grades  should  be  made  as  short  as 
possible.  While  a  horse  may  exert  two  and  one-half  times  its  normal 
pull,  this  extra  effort  cannot  be  sustained  for  long  periods  or  frequent- 
ly repeated  without  exhausting  the  horse  before  the  days  work  is 
finished. 

What  has  been  said  regarding  the  effect  of  tractive  and  grade 
resistance  on  horse  drawn  vehicles,  is  equally  true  in  its  general 
application  to  self-propelled  vehicles.  Although  the  automobile  and 
auto-truck  must  be  reckoned  with  in  highway  design,  horses  are 
still  a  big  factor  and  for  some  pavements  like  brick,  conditions  are 


28  HIGHWAY  ECONOMICS 

not  much  changed  by  the  growth  of  automobile  transportation.  The 
automobile  has  a  much  greater  reserve  power  than  the  horse  and  of 
course  can  be  made  to  surmount  comparatively  heavy  grades  with  the 
maximum  load.  This  is  done  at  a  sacrifice  of  speed  wherein  one  of 
the  chief  advantages  of  the  auto  lies  and  with  increased  consumption 


Fig-.   9 — Roanoke  Traffic  Way,  Kansas  City,  Mo.,  Brick  Road  Curved  to 
Get  Good  Grade  at  Less  Cost. 

of  fuel  and  wear  and  tear  on  the  machine.  It  is  unfortunate  that  no  re- 
liable data  regarding  the  effect  of  grade  resistance  on  automobiles  is 
available,  but  it  is  well  known  that  the  frequent  use  of  the  reserve  pow- 
er— "Low  speed" — increases  the  gasoline  consumption  and  the  wear  and 
tear  on  the  machinery  out  of  all  proportion  to  the  distance  traveled. 
The  grade  resistance,  itself,  is  the  same  for  a  given  load  regardless 


HIGHWAY  ECONOMICS  29 

of  the  motive  power  and  the  percentage  of  grade  should,  therefore, 
be  kept  at  a  minimum. 

It  is  a  noteworthy  fact  that  most  of  the  excessive  grades  on  our 
highways  could  have  been  overcome  or  avoided  without  extraordinary 
expense.  Too  much  stress  has  been  laid  on  the  straight  line  road;  the 
saving  in  distance  at  a  sacrifice  of  grade  has  been  much  overestimated. 
For  example  the  actual  distance  over  a  hill  may  be  no  less  than  the 
distance  around  the  hill;  the  road  in  one  case  being  curved  in  a  ver- 
tical plane,  in  the  other  case  in  a  horizontal  plane.  In  fact  it  is 
surprising  to  find  by  actual  measurement  how  little  is  added  to  the 
length  of  a  road  by  slight  deviations  from  a  straight  line.  Even  where 
the  straight  road  is  shorter,  the  cost  of  construction  is  frequently 
much  greater  than  for  a  road  deviating  enough  to  avoid  the  natural 
obstacles. 

The  economical  location  of  a  road  demands  that  the  interest  on 
the  cost  of  construction,  the  annual  cost  of  maintenance  and  the  cost 
of  conducting  transportation  over  it,  taken  together,  shall  be  a  mini- 
mum, and  all  of  these  factors  should  be  studied  before  deciding  on 
any  changes.  The  section  line  system  of  roads  which  is  common  in 
the  West,  though  convenient  in  many  ways,  often  makes  proper  road 
location  in  rough  country  a  difficult  matter.  Where  new  rights-of- 
way  cannot  be  exchanged  for  the  old,  it  may  be  economy  to  condemn 
a  road  in  the  new  location  as  the  money  so  spent  may  often  be 
saved  many  times  over  in  the  cost  of  construction.  It  is  also  a  great 
advantage  to  supplement  the  rectangular  road  system  by  diagonal 
highways  connecting  the  commercial  centers  by  the  shortest  routes 
consistent  with  good  grades. 

The  location  of  the  main  traveled  roads  and  the  fixing  of  the 
grades  on  the  same  is  a  delicate  and  painstaking  operation,  calling 
for  much  skill  and  study.  Highway  Engineers  would  do  well  to  study 
the  theory  of  location  of  railroads  and  learn  to  take  advantage  of  the 
natural  typography  of  the  ground. 

The  following  principles  may  be  used  as  a  guide  in  the  final 
selection  of  the  location: 

1.  Follow    the    route    giving   the    easiest    grade,    remembering 
that  the  greater  the  expected  travel  and  the  better  the  pavement  to  be 
used,  the  more  essential  is  a  low  grade. 

2.  Connect  places  of  importance  by  the  shortest  and  most  di- 
rect route  commensurate  with  low  grades. 

3.  Avoid  all  unnecessary  ascents  and  descents. 

4.  Cross  ridges  at  lowest  points  and  valleys  at  highest  points 
possible. 

5.  Avoid  obstacles  requiring  expensive  construction,  but  where 
streams,  etc.  are  encountered  cross  them  at  right  angles  in  order  to 
reduce   the   cost  of  structural   work. 

6.  Avoid  grade  crossings  of  railways. 

7.  Locate  the  center  line  with  reference  to  the  natural  surface 
in  order  to  make  the  grading  and  drainage  cost  as  cheap  as  possible. 

8.  Avoid  sharp  turns  or  turns  where  the  view  of  the  road  each 
side  of  the  turn  is  obstructed. 


30  HIGHWAY  ECONOMICS 

In  fixing  the  grades  on  the  road  the  following  fundamentals 
should  be  kept  in  mind: 

1.  Make  maximum  grades  as  short  and  infrequent  as  possible. 

2.  Provide  a  grade  for  longitudinal  drainage  on  flat  stretches 
of  at  least  one-half  of  one  per  cent,  or  provide  sufficient  capacity  and 
fall  to  the  side  ditches  to  carry  away  the  surface  drainage 'promptly. 

3.  Where  possible  keep  the  grade  slightly  above  the  adjoining 
land  to  provide  better  sub-drainage. 

4.  Establish  the  grade  line  in  such  a  manner,  consistent  with 
the  above,  that  the  fills  or  embankments  may  be  made  from  nearby 
excavations  or  cuts,  balance  the  cuts  and  fills  in  other  words. 

5.  Modify  heavy  grades  around  curves  and  avoid  steep  grades 
near  bridges,  turns,  railway  crossings,  or  intersections. 

6.  Connect   the    tangents    of   two   intersecting    grades    with   a 
vertical  curve. 

7.  Break  up  long  continuous  rises  with  level  resting  places  at 
convenient  intervals. 

Although  it  is  not  often  possible  in  towns  or  cities  to  follow 
all  the  principles  outlined  for  fixing  the  location  and  grades  of  coun- 
try roads,  they  should  be  made  to  govern  where  practical.  Improve- 
ments already  in,  and  the  effect  of  grading  on  the  abutting  property 
should,  however,  be  given  due  consideration.  On  the  main  thorough- 
fares every  attempt  should  be  made  to  secure  satisfactory  grades, 
while  on  the  side  streets  the  percentage  of  grade  may  be  of  secon- 
dary importance.  A  great  deal  of  trouble  can  be  saved  the  City  and 
a  great  deal  of  expense  to  the  property  owners,  by  fixing  the  grade  on 
all  existing  streets  whether  it  is  intended  to  actually  grade  them  soon 
or  not,  so  that  any  sidewalks  laid  or  buildings  erected  conform  to 
the  street  as  it  will  some  day  be  improved.  The  established  grades 
should  be  a  matter  of  record  in  the  city  clerk's  office  so  that  any 
competent  surveyor  can  furnish  the  property  owner  with  the  pro- 
posed elevation  of  the  street  in  front  of  his  property.  No  new  streets 
should  be  accepted  by  the  city  unless  the  location  and  grades  are 
satisfactory  and  to  the  benefit  of  the  city.  These  represent  the  funda- 
mental principles  of  city  planning  which  is  essentially  a  proper  guid- 
ing of  the  city's  growth. 

In  establishing  grades  on  streets,  attention  should  be  given  to 
surface  drainage.  Undue  concentration  of  storm  water  at  any  one 
point  should  be  avoided  as  well  as  intersections  or  places  in  the 
street  which  hold  water.  Street  intersections  should  be  as  nearly 
level  as  possible  and  the  position  of  future  catch  basins  and  lines  of 
sewers  should  be  carefully  looked  into.  Well  planned  streets  are  a 
source  of  beauty  and  satisfaction  to  a  city  that  the  residents  cannot 
afford  to  be  without.  Once  improved  it  is  scarcely  probable  that  the 
location  or  grade  of  a  street  or  road  will  ever  be  materially  changed. 
They  become  permanent  assets  and  should  be  given  all  the  study 
and  careful  consideration  possible.  The  advantages  to  be  gained  by 
improved  roads  and  streets  should  be  kept  in  mind,  so  they  can  be 
made  to  return  the  largest  dividend  in  satisfaction  and  service, 


B 


CHAPTER  III 

THE  SUB-GRADE  AND  FOUNDATION 

FTER  THE  PRELIMINARY  ENGINEERING  work  of  locating 
the  line  and  fixing  the  grade  of  the  highway  has  been  com- 
pleted, the  actual  improvement  work  may  be  commenced. 
From  one-half  to  three-quarters  of  the  cost  of  this  improve- 
ment may  be  considered  as  absolutely  permanent  and  should 
be  treated  with  all  the  care  due  a  permanent  investment.  If  design- 
ed with  a  view  to  future  needs  and  in  accordance  with  sound  engi- 
neering principles,  the  grading,  the  structural  work  and  the  pre- 
paration of  the  sub-grade  including  surface  and  sub-drainage 
should  never  need  replacement,  while  the  foundation  and  the  wear- 
ing surface  may  be  considered  more  or  less  permanent  depending  on 
the  kind  of  construction  employed  and  the  care  it  receives  in  use. 
In  many  discussions  on  street  and  road  improvement,  the  property 
owners  consider  the  surfacing  material  only,  without  realizing  that 
the  wearing  surface  is  but  a  relatively  small  portion  of  the  total  cost 
and  that  no  pavement  will  give  entire  satisfaction  unless  the  sub- 
structures are  carefully  designed  and  constructed. 

The  first  things  to  be  planned  and  'built  are  the  structures 
necessary  to  provide  for  surface  drainage  and  the  crossing  of 
streams  or  other  obstructions.  To  avoid  legal  claims  for  damages 
the  surface  drainage  should  always  be  carried  in  the  natural  chan- 
nels unless  the  consent  of  the  owners  of  property  is  obtained  for 
its  diversion.  Culverts  should  be  of  ample  capacity  to  take  the 
water  from  the  heaviest  storms.  Records  of  the  height  and  amount 
of  water  in  the  natural  drainage  channels  during  the  worst  storms 
give  the  best  means  for  determining  the  size  of  culverts  or  the 
waterway  for  bridges.  If  these  are  not  available  or  are  unreliable, 
one  of  the  many  empirical  formulae  may  be  used  when  accompanied 
by  good  judgment.  About  the  best  of  these  is  the  Burkle-Ziegler, 

4__ 

formula,      Q  =  RC    i/_s_      where  Q  is  the  cubic  feet  per  second  per 

A 

acre  reaching  the  culvert;  R  is  the  average  rainfall  rate  during  the 
heaviest  storm  in  cubic  feet  per  second  per  acre;  C  is  a  constant 
varying  from  0.75  for  paved  streets  in  cities,  or  0.62  for  ordinary 
city  streets  to  as  low  as  0.25  for  farming  country;  S  is  the  general 
fall  of  the  drainage  area  per  1,000  feet;  and  A  is  total  drainage  area 
in  acres.  In  the  absence  of  definite  records  the  average  run-off  dur- 
ing heavy  storms  is  taken  at  one  inch  per  hour.  One  inch  rain  over 
one  acre  gives  3,630  cubic  feet  so  that  this  rate  is  almost  exactly 
equivalent  to  one  cubic  foot  per  second  per  acre,  and  R  is  1.  The 
size  of  the  culvert  to  care  for  this  computed  discharge  depends  on 
the  material  used,  the  shape  and  the  grade  to  which  it  is  laid.  An- 
other formula  which  has  been  used  is  the  one  proposed  by  A.  N. 
Talbot.  The  cross  sectional  waterway  area  of  culvert  in  square  feet 

^     i/     (Drainage  area  in  Acres)  3  ^     in     tnis 

formula  is  a  variable  coefficient  which  for  steep  and  rocky  ground 
may  be  taken  at  2/3  to  1;  for  rolling  farming  country  subject  to 


32 


THE  SUB-GRADE  AND  FOUNDATION 


floods  at  times  of  melting  snow  and  with  the  length  of  valley 
three  or  four  times  its  width,  C  is  about  1/3,  and  for  longer  valleys 
and  flatter  country  without  snow  danger,  C  may  be  1/5  or  even  less. 
(See  Fig  10.)  By  checking  existing  culverts  which  have  proved 

0  4  8          £          /6         20         ?4         ?8 


0  4  8  /?          /6         ?0         24          ?8 

Cross   Sech'ona/  /4rea  ofCu/uerf  //?  Square  r~eef. 

Fig1.    10 — Culvert  Areas   by  Talbot's   Formula. 

satisfactory  with  this  formula,  values  for  C  may  be  determined  for 
use  in  designing  new  culverts  under  like  conditions.  The  formula  is 
not  difficult  of  operation  even  without  the  use  of  logarithms  when 
it  is  remembered  that  the  fourth  root  is  obtained  by  taking  the  square 
root  of  the  square  root. 


THE  SUB-GRADE  AND  FOUNDATION  33 

The  inlet  to  the  culvert  should  be  so  placed  as  to  receive  the 
water  in  a  direct  line  with  the  channel  and  it  must  be  protected  by  a 
headwall  to  prevent  the  water  washing  the  surrounding  dirt  away. 
The  inlet  should  also  be  placed  high  enough  so  that  it  will  not  fill 
up  with  mud  and  the  waterway  approaching  it  should  not  be  too 
steep,  so  as  to  prevent  the  opening  from  being  clogged  with  brush, 
leaves  and  dirt.  The  culvert  itself  must  be  as  straight  and  short  as 
possible,  and  discharge  the  water  in  the  line  of  the  natural  channel. 
No  storm  water  drain  should  be  less  than  12  inches  in  diameter  and 
18  inches  as  a  minimum  would  be  better  for  roads,  where  pipes  are 
cleaned  at  infrequent  intervals.  On  account  of  cheapness  and  per- 
manence of  construction,  drains  up  to  30  inches  in  diameter  are  usual- 
ly heavy  vitrified  clay  or  concrete  pipe  laid  with  tightly  packed 
cement  mortar  joints  and  with  small  concrete  or  brick  headwalls. 
Where  a  larger  size  is  necessary  and  two  or  three  lines  of  pipe  are 
not  advisable  it  has  been  customary  lately  to  build  some  form  of  box 
or  arch  reinforced  concrete.  While  this  is  satisfactory  it  may 
frequently  be  found  cheaper  to  construct  culverts  up  to  20  foot 
spans  as  brick  arches  sprung  from  brick  or  rubble  masonry  side 
walls,  thus  utilizing  materials  at  hand  and  eliminating  expensive  form 
work  and  the  procuring  and  cutting  of  various  sizes  of  reinforcing 
metal. 

Brick  masonry  is  permanent  and  there  is  little  chance  of 
failure;  it  can  be  placed  by  small  gangs  of  workmen  in  a  short 
time  and  with  a  minimum  of  equipment  and  material.  The  portions 
of  the  kilns  of  paving  brick  not  suitable  for  paving  purposes  can  be 
used  at  low  cost  to  advantage  in  this  work,  and  the  chipped  or 
broken  paving  brick  make  ideal  floors  for  culverts.  The  table  shown 
gives  the  proper  thickness  of  the  brick  arching  and  size  of  abut- 
ments for  different  spans.  Where  rough  rubble  masonry  is  used  for 
the  side-walls  the  thickness  shown  should  be  increased  10  to  20%. 
All  work  and  materials  are  assumed  to  be  first  class  and  all  joints 
filled  with  one  to  three  Portland  cement  mortar.  Where  paving 
brick  with  lugs  are  used,  the  lugs  should  be  turned  so  as  not  to  re- 
ceive the  bearing. 

TABLE  OF  PRINCIPLE  DIMENSIONS  OF  SEGMENTAL  BRICK 
ARCH  CULVERTS. 

Maximum  Minimum 

Thickness                   Height  of  Thickness  of 

Span  in                             of                           Abutment  Abutment 

Feet                          Arch  Ring                     in  Feet  for  Arches 

in  Inches                  for  Minimum  of!20Deg. 

Thickness  in  Feet 

3  ft.  8  in.  2.5  2.0  9.3 

4  8  3.0  2.3  15.3 
6                              12                                 3.8                         3.0                     30.2 
8                              12                                 4.6                          3.7  49.9 

10  16  4.8  4.2  68.5 

12  16  5.2  4.5  91.9 

14  20  5.7  4.7  120.0 

16  20  6.0  4.9  148.5 

18  24  6.3  6.1  179.8 

20  24  6.6  6.3  214.0 


THE  SUB-GRADE  AND  FOUNDATION  35 

All  culverts  unless  specially  designed  for  concentrated  loads 
should  have  at  least  one  foot  of  earth  covering  on  top  of  them.  When 
the  headroom  available  is  insufficient  to  permit  of  the  larger  sizes 
of  arch  culverts,  two  or  more  small  sized  lines  may  be  built  or  a  re- 
inforced concrete  girder  bridge  may  prove  economical  for  spans  from 
15  to  >50  feet.  In  all  cases  care  must  be  taken  to  provide  adequate 
foundations  extending  below  the  frost  line,  abutments  capable  of 
withstanding  the  arch  thrust,  and  well  tamped  earth  on  each  side 
before  filling  on  top  of  the  arch.  Ample  provision  should  be  made 
against  washout  of  either  the  culvert  itself  or  the  road  by  suit- 
able parapet  and  wing  or  headwalls.  Spans  of  over  35  feet  and  over 
streams  or  other  obstructions  are  classed  as  bridges  and  require 
special  treatment.  For  permanence  and  low  cost  of  maintenance,  re- 
inforced concrete  has  won  a  well  deserved  reputation  for  this  class 
of  work.  Where  it  is  desired  on  account  of  its  location  to  empha- 
size the  aesthetic  qualities  of  a  bridge,  its  beauty  has  frequently 
been  much  enhanced  by  the  use  of  brick  paneling,  coping  or  facing. 
The  brick  facing  for  the  exposed  surfaces  may  often  be  laid  up  in- 
side the  wooden  forms,  provision  being  made  for  proper  bond  to 
the  reinforced  concrete  which  is  placed  afterwards. 

The  actual  work  of  grading  the  street  or  road  is  usually  car- 
ried on  immediately  following  the  surface  drainage  structural  work. 
In  addition  to  seeing  that  the  grading  is  carried  to  the  full  width 
and  to  the  proper  level,  attention  must  be  paid  to  a  number  of 
other  points.  The  sides  of  deep  cuts  should  be  given  enough  slope 
so  that  they  will  not  wash  down  into  the  ditches.  Rock  excavation 
should  be  carried  low  enough  to  provide  for  at  least  six  inches 
of  backfilled  earth  between  the  rock  and  the  pavement  foundation, 
and  the  surface  of  the  rock  should  be  left  so  that  it  will  not  hold 
large  pockets  of  water.  Fills  of  more  than  four  feet  in  depth 
should  be  made  in  not  over  four  foot  layers  and  each  layer  should 
be  carried  out  the  full  width  of  the  fill  to  the  side  slopes.  Dumping  of 
earth  for  a  fill  over  the  end  or  sides  will  not  thoroughly  compact  the 
embankment  and  the  fill  may  continue  to  settle  for  several  years.  The 
fills  should  be  brought  up  on  the  sides  at  a  slope  which  will  insure 
stability  of  material,  in  any  case  not  less  than  one  and  one-half 
feet  horizontal  to  one  foot  vertical  rise.  If  rock  is  used  in  making 
fills,  about  equal  quantities  of  earth  should  be  mixed  with  it,  but 
logs,  brush  or  other  perishable  material  should  not  be  allowed  to 
remain.  Fills  made  on  a  side  hill  often  require  that  the  original  ground 
surface  be  ploughed  and  stepped  to  prevent  the  slipping  of  the  new 
material.  Where  fills  of  less  than  one  foot  are  made  the  original 
surface  should  be  ploughed  so  that  the  new  material  will  knit  with 
the  old.  It  is  to  be  expected  that  embankments  of  all  heights  will 
settle  about  10%  of  their  height  the  first  year  after  construction, 
but  of  course  this  will  vary  with  the  care  used  in  building  them, 
the  season  of  the  year  and  the  kind  of  soil.  For  this  reason  where 
there  are  many  fills  over  five  or  six  feet  deep  the  grading  should  be 
completed  if  possible  a  year  in  advance  of  the  paving.  Some  cities 
have  gone  to  the  expense  of  compacting  heavy  fills  as  they  are  made 
in  thin  layers  with  a  steam  roller  so  that  the  paving  could  follow 
immediately. 

Ample  side  ditches  should  be  provided  for  surface  and  sub- 
drainage  water,  and  these  should  discharge  as  frequently  as 


36 


THE  SUB-GRADE  AND  FOUNDATION 


possible  into  the  natural  watercourses  so  as  to  avoid  having  the  side 
ditches  carry  the  storm  water  any  great  distance  or  in  any  great 
volume.  Frequently  the  side  gutters  must  take  not  only  the  storm 
water  which  falls  on  the  road  itself  but  also  the  water  from  the 
adjoining  land,  and  this  condition  must  be  recognized  in  designing 
the  side  ditch.  Where  there  is  danger  of  the  ditches  being  washed 


-  —r*  —Marrow  Section  for  Deep  Cut 

Cross  \5ec//0/7  of/SfvofMo/w/tfhic  Br/c/c  &o&d '  /v  Ct/f. 


br&7 

.  ^    \^y  '. '.  /"^  ,-* .—  *-«  /^  t 


4"*4y^ 

////-  ^-Narrow  Sec  f /on  on  r/eavy  r77f 
Cross  Section  of /0  foot  Brick 

Pig.    12 — Brick    Road    Cross    Sections. 


out  on  account  of  the  steepness  of  the  grade,  low  rock  dams  should 
be  built  across  the  ditch  at  frequent  intervals,  or  the  sides  and  bot- 
tom riprapped  with  heavy  stone. 

It  always  pays  to  be  certain  that  the  surface  water  will  be 
quickly  and  safely  removed  from  the  road  or  street.  When  not  prop- 
erly handled,  it  frequently  causes  very  serious  and  expensive  damage. 

In  spite  of  all  that  has  been  written  or  said  in  regard  to 
proper  sub-drainage  for  pavements,  this  important  feature  is  too 
often  disregarded  or  ineffectively  handled.  This  is  probably  because 
no  hard  and  fast  rules  can  be  laid  down  to  cover  this  part  of  the 
work,  but  each  case  must  be  treated  individually  and  in  accordance 
with  the  experience  and  best  judgment  of  the  Engineer.  In  the  first 
place  care  must  be  taken  to  prevent  any  surface  water  reaching  the 
sub-grade.  The  system  of  sub-drainage  should  be  designed  to 


THE  SUB-GRADE  AND  FOUNDATION  37 

promptly  remove  all  ground  water  for  a  depth  of  at  least  two  feet  be- 
low the  surface  of  the  pavement.  This  will  prevent  the  sub-grade 
from  becoming  softened  or  heaved  by  frost.  The  load  a  given  soil 
will  support  depends  on  the  amount  of  moisture  in  it.  Coarse  sand 
and  gravel  are  practically  self-draining  and  when  there  is  an  imper- 
vious pavement  to  prevent  surface  water  reaching  the  sub-grade 
the  only  precaution  necessary  is  to  see  that  ground  water  from  the 
sides  of  the  cuts  and  any  springs  are  taken  care  of.  The  difficulty 
of  sub-drainage  varies  with  the  character  of  the  soil,  fine  sandy 
loam  on  account  of  its  capillary  action  and  stiff  clay  being  the  most 
difficult.  The  clay  and  gumbo  soils,  because  of  their  low  load  sup- 
porting power  even  when  dry,  and  because  of  the  difficulty  in  re- 
moving the  moisture  from  them,  require  the  most  careful  attention. 

The  drainage  of  the  sub-grade  is  usually  accomplished  by  a 
system  of  lines  of  clay  or  cement  tile  laid  in  trenches  three  lor 
four  feet  deep,  although  where  rock  is  plentiful,  stone  spalls  and 
boulders  may  be  used  as  a  "blind"  drain  instead  of  the  tile.  In 
towns  or  cities  where  there  are  no  side  ditches,  the  lines  of  tile 
are  laid  parallel  to  the  curbing  and  connected  to  manholes  or  catch 
basins  at  frequent  intervals.  On  country  roads,  paved  not  more  than 
20  feet  wide,  the  drain  tile  are  usually  laid  longitudinally  under  one 
or  both  sides  of  the  pavement  and  having  outlets  in  the  side  ditches 
or  surface  drainage  culverts.  The  drain  tile  is  usually  four  to  eight 
inches  in  diameter  and  outlets  are  provided  and  the  lines  are  spaced 
close  enough  together  to  care  for  the  expected  ground  water  with 
the  size  of  pipe  selected.  Drains  smaller  than  four  inches  should 
not  be  used  as  they  have  a  tendency  to  silt  up.  They  are  laid  in 
trenches  of  at  least  two  feet  in  width  butt  jointed,  carefully  graded 
to  the  outlets  and  covered  with  stone  spalls,  small  boulders,  coarse 
gravel  or  other  porous  material.  If  possible  the  entire  trench  should 
be  backfilled  with  coarse  material,  but  in  any  case  broken  stone  or 
other  coarse  material  should  be  placed  for  a  depth  of  at  least  one 
foot  over  the  top  of  the  tile  and  the  full  width  of  the  trench.  The 
outlets  should  be  carefully  protected  from  breakage  and  covered  with 
wire  netting  to  prevent  the  ingress  of  vermin.  Drains  should  be 
laid  at  least  2  feet  below  sub-grade  and  4  feet  is  often  better.  The 
depth  of  drains  is  an  important  factor  in  determining  the  area 
drained  and  also  the  uniformity  of  drainage. 

Determining  where  sub-drain  tile  are  necessary  requires  care- 
ful study  and  a  thorough  knowledge  of  soil  conditions  during  all 
seasons  of  the  year.  Cuts,  the  upper  side  of  side-hill  roads,  low 
ground,  springs  and  boggy  sections  nearly  always  require  some  un- 
derdrainage.  Since  the  expense  of  construction  is  light,  it  is  best  to 
be  on  the  safe  side  and  install  drain  tile  in  all  cases  of  doubt. 

It  should  be  remembered  that  the  sub-grade  is  what  must 
finally  carry  all  loads.  The  pavement  foundation  simply  distributes 
the  load  over  a  sufficient  area  of  sub-grade.  By  providing  a  sub-grade 
of  uniform  density  and  of  proper  grade  and  cross  section,  by  exclud- 
ing the  surface  water  with  an  impervious  pavement  and  by  promptly 
removing  the  seepage  and  ground  water,  the  bearing  power  of  soils 
is  increased  from  three  to  ten  times  with  a  corresponding  saving  in 
the  amount  and  cost  of  the  pavement  foundation. 

After  excavating  the  sub-grade  to  a  uniform  grade  and  crown 
it  should  be  rolled  with  a  heavy  roller.  The  rolling  will  compact 


38  THE  SUB-GRADE  AND  FOUNDATION 

the  upper  soil  layer  and  iron  out  small  unevenesses,  but  must  not  be 
depended  upon  to  sufficiently  compact  trenches  or  deep  fills.  Its 
chief  functio'n  should  be  to  discover  soft  spots  and  variations  in  the 
bearing  power  of  the  sub-grade.  These  places  must  be  dug  out 
and  backfilled  with  other  material  or  stiffened  by  the  addition  of 
broken  stone,  cinders  or  sand,  so  that  the  roller  will  finally  indicate  a 
uniformly  compacted,  firm,  unyielding  sub-grade.  Before  the  final 
passage  of  the  roller,  it  is  well  to  drag  the  sub-grade  with  a  templet 
in  order  to  level  up  the  depressions  and  bumps.  This  will  save  in  the 
amount  of  foundation  and  insure  a  uniform  thickness.  A  sub-grade 
prepared  with  the  care  indicated  above  will  support  from 
one-half  to  eight  tons  per  square  foot  depending  on  the  nature  of 
the  soil.  On  the  uniformity  of  the  bearing  power  which  can  be 
developed  from  the  sub-grade  depends  in  a  great  measure  the  quality 
and  thickness  of  the  pavement  foundation. 

The   purposes    of   a   foundation   may   be   itemized   as   follows : 

(1)  to  distribute  the  wheel  loads  over  a  sufficient  area  of  the  sub- 
grade  so  that  the  bearing  power  of  the  soil  will  not  be  exceeded; 

(2)  to  bridge  over  soft  spots  in  the  sub-grade;   (3)  to  provide  a  rigid, 
uniform  bed  for  the  laying  of  the  wearing  surface,  and   (4)   to  pro- 
tect the  wearing  surface  both  by  the  absorbtion  of  shocks  due  to  the 
impact  of  swiftly  moving  loads   and  by  maintaining  the   surface  to 
uniform  grade  and  crown  without  undue  deflection  under  the  heaviest 
loads.     To   accomplish   these   purposes,    sand,    gravel,   crushed    rock, 
brick,  concrete  and  other  materials  have  been  used.    On  account  of 
its    cheapness,    ease    of    construction    and    great    strength,    Portland 
Cement  concrete  is  much  the  best  under  modern  traffic  conditions. 
Where  some  of  the  functions  of  the  foundation,  however,  can  be  com- 
bined with  the  wearing  surface  as  in  monolithic  brick'  pavement,  old 
macadam,  gravel  or  crushed  rock  may  be  used.     It  is  much  more  diffi- 
cult and  frequently  as  expensive,  however,  to  properly  prepare  such 
a  base  as  to  lay  a  concrete  foundation  of  equal  or  greater  strength. 

The  thickness  of  the  concrete  base  necessary  to  answer  the 
purposes  for  which  a  paving  foundation  is  intended,  is  therefore,  en- 
tirely a  matter  of  engineering  design  and  depends  on  the  character 
of  the  sub-grade  and  the  care  used  in  its  preparation,  on  the  weight 
and  kind  of  traffic,  on  the  surfacing  material  used,  and  on  the 
strength  and  quality  of  the  concrete  itself  as  determined  by  the  quali- 
ty of  the  aggregate,  the  amount  of  cement  used  and  the  care  in  its 
construction.  It  is  as  meaningless  to  say  that  all  pavements  should 
have  a  six  inch  concrete  foundation  as  that  all  shoes  shall  be  No. 
8  size.  The  base  must  be  designed  to  fit  the  individual  case. 

There  are  many  cases  where  a  six  inch  foundation  is  inade- 
quate and  other  cases  where  it  is  stronger  than  necessary.  Unfortu- 
nately errors  in  foundation  design  and  construction  have  been  nu- 
merous and  fully  one-half  of  the  defects  in  pavement  can  be  traced  to 
carelessly  or  improperly  built  foundations.  There  is  no  reason, 
however,  why  a  four  or  five  inch  foundation  under  favorable  soil 
conditions  should  not  be  ample  for  moderate  traffic  on  country  roads, 
provided  extreme  care  is  taken  in  the  preparation  of  the  sub-grade 
and  in  the  mixing  and  placing  of  the  concrete.  On  the  other  hand 
streets  under  continuous,  heavy,  swiftly  moving  traffic  in  a  large 
city  where  the  pavement  is  being  constantly  opened  for  sewer  and 


THE  SUB-GRADE  AND  FOUNDATION  39 

water  connections  and  where  sub-grade  conditions  are  unfavorable, 
may  require  a  mass  and  strength  of  foundation,  obtained  only  by  a 
thickness  of  concrete  of  eight  to  ten  inches.  Intead  of  adopting  a 
universal  thickness  for  the  concrete  base  on  any  one  highway,  it 
might  be  economy  in  some  cases  to  vary  the  depth,  using  a  heavier 
base  on  the  portions  of  the  road  where  the  sub-grade  was  more  un- 
certain and  difficult  to  drain.  As  a  general  rule,  however,  it  is  better 
to  have  a  thicker  base  of  a  lean  mixture  than  a  thin  base  of  a  rich 
mixture.  The  strength  of  the  base  acting  as  a  beam  varies  as  the 
square  of  the  depth,  so  that  concrete  of  the  same  proportions  is  over 
twice  as  strong  in  a  six  inch  base  as  in  a  4  inch  base,  and  four 
times  as  strong  as  in  a  3  inch  base.  In  other  words  the  proportions 
of  the  concrete  might  be  adjusted  so  as  to  give  a  unit  strength  in  the 
6  inch  base  of  only  one-fourth  the  unit  strength  of  the  3  inch  base 
and  yet  both  would  be  equally  capable  of  carrying  loads  over  soft 
spots  in  the  sub-grade.  The  thicker  base  would  moreover  have  twice 
the  weight  or  mass  for  absorbing  the  shocks  and  vibrations  due  to 
rapidly  moving  traffic,  an  important  item  not  usually  considered  in 
highway  design.  The  saving  in  cement  and  labor  would  probably  not 
entirely  offset  the  additional  cost  of  sand  and  rock,  but  where  the 
latter  may  be  had  at  average  prices,  a  1-4-8  concrete  6  inches  thick 
can  be  placed  at  about  '50%  increase  in  cost  over  a  1-2-3  concrete  3 
inches  thick,  and  the  thicker  base  will  be  one-third  stronger  acting  as 
a  beam.  A  slight  defect  or  any  lack  of  uniformity  in  the  concrete 
is  much  more  serious  in  a  thin  base  and  consequently  greater  care 
must  be  used  in  mixing  and  placing  the  concrete  and  in  preparing  the 
sub-grade. 

The  wearing  surface  selected  and  the  method  of  laying  it,  also 
influences  the  depth  of  foundation  required.  It  is  evident  that  a 
cement  grouted  brick  which  distributes  the  concentrated  wheel  loads 
over  a  considerable  area  of  the  top  surface  of  the  base  will  require 
less  strength  in  the  base,  than  a  thinner  wearing  surface  which  has 
no  distributive  effect.  A  pavement  which  presents  a  smooth  uniform 
surface  will  also  reduce  the  impact  shocks  of  swiftly  moving  traffic 
and  require  les^  foundation  than  one  which  is  forever  out  of  repair, 
uneven,  loosened  or  full  of  depressions. 

The  advent  of  the  motor  truck  with  its  extremely  heavy  loads 
carried  at  comparatively  high  speed  has  complicated  the  foundation 
problems  of  the  highway  engineer.  Where  formerly  the  heavily 
laden  farm  wagon,  giving  a  load  on  the  surface  of  the  pavement  of 
about  350  pounds  per  inch  width  of  tire  and  moving  at  3  to  5  miles 
per  hour,  was  about  as  heavy  as  the  pavement  was  required  to  care  for, 
now  truck  loads  of  5  to  10  tons  moving  at  15  to  25  miles  an  hour  and 
giving  loads  of  from  500  to  1,200  pounds  per  inch  width  of  tire  are 
not  uncommon.  The  engineer  must  bear  these  changed  conditions  in 
mind  in  designing  his  pavements.  Even  the  best  constructed  pave- 
ment cannot,  however,  withstand  the  continuous  abuse  some  of  them 
are  being  subjected  to,  and  it  will  be  necessary  in  order  to  preserve 
the  investment  of  the  taxpayer  for  the  use  of  the  many,  to  prevent  by 
strict  regulation  the  improper  use  of  our  pavements  by  the  few. 
Every  community  should  have  a  law  regarding  width  of  tires  on  ve- 
hicles, prohibiting  a  greater  load  than  700  or  800  pounds  per  inch 
width  of  tire,  which  will  correspond  to  a  9  ton  load  distributed  on 
four  wheels  with  6  inch  width  of  tires.  The  speed  for  the  maximum 


40 


THE  SUB-GRADE  AND  FOUNDATION 


load  should  be  limited  say  to  12  miles  per  hour  and  the  maximum 
speed  for  the  lightest  loads  should  not  be  more  than  can  be  con- 
sidered safe  to  other  traffic.  License  fees  should  also  be  graded  in 
accordance  with  the  capacity  of  the  vehicle  and  the  weight  per  inch 
width  of  tire  making  the  rate  so  high  for  the  excessive  loads  that  it 
will  discourage  their  use.  All  proper  means  should  be  made  to  regu- 
late the  traffic  and  enforce  a  reasonable  law  regarding  loads.  The 
Engineer  can  then  have  some  basis  for  economical  design  and  our 
streets  and  roads  will  not  be  damaged  by  the  few  users  who  do  not 
have  properly  designed  vehicles.  Tractors  with  iron  lugs  on  the 
wheels  should  not  be  allowed  to  use  any  pavement  unless  the 
wheels  are  first  banded  or  planks  are  laid  for  them  to  travel  on. 


rope  fcu/rag  7e/7?p0fe 


Fig.  13 — An  Essential  Tool  for  Good  Pavement  Construction. 

In  the  actual  construction  of  the  concrete  foundation  on  the 
rolled  sub-grade  there  are  a  great  many  things  to  watch.  The  cement 
must  be  of  good  quality  and  sound,  the  sand  clean  and  coarse,  and 
the  crushed  stone  or  gravel  clean,  properly  sized  and  sound.  These 
must  be  combined  with  clean  water  into  a  homogeneous  mixture  of 
the  right  consistency  and  proportions,  and  spread  on  the  sub-grade  to 
a  uniform  thickness  with  the  top  smoothed  and  leveled  true  to  grade 
and  crown.  The  usual  proportions  for  the  foundation  are  one  part 
cement,  three  parts  sand  and  five  or  six  parts  broken  stone  or  gravel, 


THE  SUB-GRADE  AND  FOUNDATION 


41 


although  there  should  be  no  hesitancy  on  the  part  of  the  engineer  to 
vary  from  these  proportions  if  strong  enough  concrete  can  be  obtained 
at  lower  cost,  or  if  reduced  thickness  requires  a  richer  mixture  and 
more  strength.  Bank  run  gravel  should  never  be  used  without  screen- 
ing and  recombining  the  sand  and  coarse  gravel  in  proper  proportions. 
The  crushed  stone  and  gravel  should  be  screened  of  all  sizes  that  will 
pass  a  quarter  inch  screen  and  the  size  of  the  largest  fragment  should 
not  be  more  than  one-half  the  thickness  of  the  concrete  base.  The 
more  uniformly  the  sizes  are  graded  between  these  limits,  the  denser 
and  stronger  the  concrete  and  the  easier  it  can  be  worked  and  laid. 
There  is  a  tendency  among  the  contractors  to  hurry  the  time  of  mixing 
the  ingredients  by  adding  an  excess  of  water.  No  mixer  should  be 
allowed  into  which  the  concrete  ingredients  including  the  water  can- 
not be  accurately  measured  and  a  minimum  time  limit  should  be  fixed 
for  mixing  each'  batch.  A  little  experimenting  in  longer  mixing  and 
the  use  of  less  water  will  produce  surprising  results  in  the  quality  of 
the  concrete.  To  avoid  shoveling  and  mixing  with  dirt,  the  concrete 
should  be  deposited  from  the  mixer  close  to  its  final  position  in  the 
foundation,  leveled  off  and  tamped  to  a  dense,  uniform,  quaking  mass. 
Where  there  are  no  curbs  or  where  the  curbing  is  constructed  at  the 
same  time  as  the  foundation  it  is  necessary  to  have  side  forms  set  in 
advance  of  the  concrete.  With  a  little  care  in  setting,  these  forms 
can  be  used  as  a  guide  for  the  templets  to  level  the  sub-grade  and  the 
top  of  the  concrete  foundation.  The  use  of  a  templet,  the  ends  of 


y. '  avdv  iw®^*™'' 
fefell  '\+-2*2S 

\  every  5  fee/' 


of 


V 

Fig.  14 — Support  for  Templet  in 
Center  of  Wide  Street  or  Where 
Curbs  are  Uneven. 

which  rest  on  side  forms  set  to  line  and  grade  or  on  the  curbs,  for 
finishing  the  surface  of  concrete  foundations  is  strongly  recommended. 
(See  Fig.  13).  In  no  other  practical  way  can  a  more  uniform  thick- 
ness or  surface  finish  to  the  concrete  base  be  secured.  Even  where 
the  coarse  aggregate  in  the  concrete  is  too  large  or  angular  to  per- 
mit dragging  the  concrete  with  the  templet,  it  can  be  used  as  a  guide 
to  the  leveling,  as  a  tamp  and  to  test  the  trueness  of  the  surface. 
The  templet  should  be  substantially  constructed  of  wood  or  steel  and 
cut  or  bent  to  accurately  fit  the  proposed  upper  surface  of  the  foun- 
dation when  resting  on  the  curbing  or  side  forms.  On  wide  streets  it 
may  be  necessary  to  place  a  longitudinal  guide  strip  along  the  center 
line  and  use  two  templets,  the  center  form  being  removed  as  fast  as 
the  concrete  is  placed.  (See  Fig.  14.)  The  templet  saves  the  con- 
tractor a  great  deal  of  time  and  waste  material  and  makes  if  easier 


42  THE  SUB-GRADE  AND  FOUNDATION 

to  lay  the  wearing  surface  while  it  insures  the  engineer  a  uniform 
thickness  of  foundation  and  a  true  and  even  surface  for  his  pavement, 
two  essentials  of  durability.  In  the  laying  of  monolithic  brick  pave- 
ments, which  will  be  described  in  a  later  chapter,  a  templeted,  uniform 
foundation  surface  is  absolutely  necessary. 

After  the  concrete  has  been  placed,  care  must  be  exercised  to 
see  that  it  is  not  disturbed  while  gaining  strength  and  that  it  re- 
ceives sufficient  moisture  to  develop  its  full  strength.  In  dry,  warm, 
weather  the  sub-grade  should  be  well  soaked  with  water  in  advance 
of  the  laying  of  the  concrete,  and  the  finished  concrete  should  be 
protected  from  drying  out  by  covering  with  water,  moist  earth  or  by 
frequent  sprinkling.  These  precautions  can  be  easily  taken  and  are 
essential  to  proper  curing.  It  should  be  borne  in  mind  that  cement 
gains  strength  very  slowly  at  low  temperatures;  scarcely  at  all  below 
40  degrees  F.  For  that  reason  the  length  of  the  period  of  curing 
will  depend  on  the  weather  conditions.  Under  the  most  favorable 
conditions  at  least  ten  days  should  elapse  between  the  time  of  the 
placing  of  concrete  and  the  permitting  of  traffic  on  the  finished 
pavement,  and  much  would  be  gained  by  lengthening  this  period. 
Time  should  be  given  for  the  concrete  to  attain  a  large  share  of  its 
maximum  strength.  The  laying  of  the  brick  wearing  surface  can  pro- 
ceed, of  course  in  the  interval  and  after  the  base  has  attained  strength 
enough  to  sustain  the  roller. 

To  summarize  this  chapter,  therefore,  emphasis  should  be  laid 
on  the  following  important  points: 

Streets  and  roads  should  be  graded  in  a  permanent  manner  and 
precautions  taken  against  undue  settlement  of  fills  or  slipping  of  the 
sides  of  cuts.  The  surface  drainage  should  be  taken  care  of  by  ample 
side  ditches,  catch-basins,  sewers  and  culverts,  all  built  -in  a  permanent 
manner  and  with  a  view  to  the  prompt  removal  of  all  storm  water 
without  damage  to  the  highway  or  the  abutting  property. 

Since  the  sub-grade  ultimately  carries  all  loads  on  the  pave- 
ment and  since  its  sustaining  power  varies  inversely  with  its  satura- 
tion, great  care  should  be  taken  in  it's  preparation.  By  means  of 
permanent,  well  designed  systems  of  sub-drainage,  all  ground  water 
should  be  removed,  and  by  care  in  rolling,  the  entire  sub-grade  must 
be  brought  to  a  uniform  surface  of  equal  bearing  power  throughout. 

While  other  forms  of  foundation  may  be  used  successfully  under 
proper  soil  conditions,  the  cement  concrete  base  is  usually  the  best 
and  most  economical.  By  varying  the  thickness  and  the  proportions 
of  the  ingredients,  a  foundation  can  be  designed  capable  of  taking 
care  of  all  conditions  of  soil  and  traffic,  and  suitable  for  fully  de- 
veloping the  wearing  qualities  of  the  pavement  surfacing. 

Care  must  be  exercised  in  the  selection  of  the  ingredients  of 
the  concrete  and  in  its  mixing,  placing  and  curing,  so  that  the  money 
invested  will  return  the  largest  dividends  in  a  dense,  homogeneous 
concrete  of  uniform  thickness  and  with  the  strength  developed  to  the 
fullest  extent. 

The  design  and  supervision  of  the  construction  of  pavement 
foundations  call  for  the  best  judgment  and  thought  of  the  trained 
engineer.  By  giving  the  strictest  attention  to  every  detail,  founda- 
tions may  frequently  be  constructed  at  less  cost  than  the  present 
standard  and  at  the  same  time  avoid  many  of  the  defects  which  now 
occur. 


CHAPTER  IV 

MANUFACTURE  OF  PAVING  BRICK 

EILTHOUGH    THE    HIGHWAY    engineer    cannot   be    expected    to 
master  all  the  mass  of  technical  detail  involved  in  the  manu- 
I    facture  of  paving  brick,  a  thorough  understanding  of  the  fun- 
damental principles  and  general  processes  is  practically  nec- 
essary if  he  expects  to  construct  the  best  brick  pavements.    A 
knowledge  of  the  working  of  a  brick  plant  will  enable  the  engineer 
to  judge  the  material  to  better  advantage,  and  to  lay  it  with  greater 
assurance  of  securing  a  satisfactory  pavement. 

The  manufacture  of  brick  is  one  of  the  oldest  industries  known. 
The  making  of  paving  brick  is  a  more  recent  outgrowth  of  the  parent 
industry,  which  was  fostered  by  the  brick  men  who  saw  in  the  dura- 
bility of  the  early  brick  pavements  an  increasing  demand  for  brick 
made  especially  for  paving  purposes.  Paving  brick  manufacture  has 
since  attained  considerable  importance  in  the  clay  products  line  and 
has  become  a  highly  specialized  branch  of  the  brick  industry  calling 
for  the  best  technical  advice  and  expert  management.  It  used  to  be 
thought  that  anyone  could  start  a  brick  plant  near  any  convenient  bed 
of  shale  or  clay,  and  with  temporary  equipment  and  cheap  labor,  turn 
out  a  brick  suitable  for  either  buildings  or  pavements.  Engineers 
began,  however,  to  discriminate  in  the  quality  of  the  brick  they  used 
for  paving,  and  the  manufacturer  was  obliged  to  call  in  the  me- 
chanical engineer  and  ceramic  expert  to  devise  machinery  and  means 
for  increasing  the  quality  and  uniformity  of  his  product. 

Since  the  manufacture  of  brick  is  not  based  on  any  secret  or 
patented  process  and  the  raw  materials  are  found  in  nearly  all  sec- 
tions of  the  country,  the  use  and  sale  of  the  finished  product  depend 
entirely  on  furnishing  the  best  material  at  the  lowest  price.  This 
has  necessitated  a  more  permanent  plant  construction,  the  installa- 
tion of  additional  machinery  and  many  labor  and  fuel  saving  devices, 
and  the  employment  ,of  higher  priced  labor  and  management. 

In  this  keen  competition  for  business,  the  quality  and  uniformity 
of  paving  brick  have  been  brought  to  a  high  state  of  perfection 
without  a  corresponding  increase  in  price.  A  study  of  the  various 
operations  in  a  modern  brick  plant  to  which  the  raw  material  is  sub- 
jected before  it  is  ready  to  lay  in  the  street  is  not  only  interesting 
but  instructive. 

Clays  are  formed,  geologically,  in  former  river,  lake  or  sea 
beds  by  deposits  of  a  silicate  of  alumina  usually  mixed  with  other 
substances.  Brick  clays  are  generally  obtained  from  former  sea  beds 
and  are  the  most  extensive  and  the  most  uniform  both  in  depth  and 
quality. 

Shale  from  which  the  majority  of  paving  brick  are  manufactured, 
is  clay  which  has  been  consolidated  by  great  natural  pressure.  Brick 
clays  or  shales  must  possess  a  certain  amount  of  plasticity  in  order  to 
be  workable.  Plasticity  of  clay  is  a  characteristic  which  distinguishes 
it  from  nearly  all  other  mineral  substances  and  may  be  defined  as 
the  property  of  a  body  which  enables  it  to  absorb  water  in  such  a 


44  MANUFACTURE  OF  BRICK 

manner  that  the  properly  moistened  body  yields  to  mechanical  pres- 
sure, but  when  the  pressure  is  removed,  the  shape  of  the  body  re- 
mains as  though  the  pressure  were  still  acting  on  it.  Some  clays  are 
deficient  in  plasticity  and  are  called  "lean,"  others  are  over-plastic  and 
are  called  "fat."  By  proper  mixing  of  clays  or  other  material  it  is 
often  possible  to  obtain  a  suitable  product  from  clay  beds  which 
would  otherwise  not  be  workable. 

The  plasticity  of  shales  must,  of  course,  be  developed  by  grind- 
ing. The  other  properties  of  a  clay  or  shale  which  make  it  suitable 
for  any  particular  class  of  brick  are  due  in  large  measure  to  the  im- 
purities contained,  such  as  ferric  oxide,  lime,  silica,  magnesia,  potash 
and  soda.  Some  of  these  act  as  fluxing  agents  and  determine  the 
temparaure  at  which  the  clay  vitrifies ;  others  prevent  warping,  shrink- 
ing and  cracking,  and  still  others  add  toughness  and  hardness  to  the 
brick.  The  iron  oxide,  for  example,  besides  acting  as  a  fluxing  agent 
for  the  silica,  is  responsible  for  the  red  color  and  increases  the 
toughness.  The  shade  or  color  is  determined  more  by  the  form  in 
which  the  iron  occurs  than  the  amount  and  also  by  the  method  of 
burning,  by  the  fuel  used  and  by  other  factors. 

While  certain  fundamental  properties  must  be  possessed  by  a 
clay  or  shale  suitable  for  the  manufacture  of  paving  brick,  as  will 
be  seen  later,  the  physical  characteristics  may  vary  considerably 
among  different  beds  and  in  different  parts  of  the  country.  Each 
bed  of  shale  has  its  own  peculiarities,  which  must  be  recognized  in 
handling  it  to  the  best  advantage.  Consequently  the  details  of  the 
methods  of  manufacture  at  different  brick  plants  will  vary.  What  is 
said  therefore  regarding  the  process  of  manufacture  covers  the  gen- 
eral practice  of  the  average  case,  and  cannot  take  account  of  the 
many  variations  necessary  in  the  details. 

The  clay  or  shale  is  usually  taken  from  a  pit  or  quarry  by 
blasting,  steam  shovel  or  mining  methods.  Care  must  be  exercised 
in  balancing  the  natural  variations  of  the  bed  so  that  the  mixture  de- 
livered to  the  mill  is  a  uniform  product.  The  shale  is  then  crushed 
if  necessary  and  delivered  to  the  dry-pan,  a  circular  pan  with  per- 
forated bottom  revolving  beneath  two  heavy  rolls.  As  a  general  rule 
the  shale  should  be  rather  finely  ground  and  screened  over  a  screen 
or  riddle  having  the  proper  sized  openings  as  determined  by  the 
physical  characteristics  of  the  shale.  Excessive  fineness  may  cause 
checking  or  cracking  in  drying  and  aggravate  laminations,  while  ex- 
cessive coarseness  will  not  develop  the  necessary  plasticity.  The 
screen  in  different  plants,  therefore,  vary  in  size  from  4  to  12  meshes 
per  lineal  inch.  The  material  then  goes  to  the  pug  mill  or  mixer,  a 
long  trough-like  machine  with  a  revolving  shaft  carrying  a  number 
of  blades  through  the  center,  where  the  ground  material  is  tempered 
and  thoroughly  mixed  with  water.  In  general  the  more  the  ground 
material  is  worked  especially  after  the  water  has  been  added  the  more 
plastic,  uniform  and  reliable  the  brick.  The  amount  of  water  added 
must  be  very  carefully  watched  as  it  is  desirable  to  get  a  uniform 
product  which  can  be  properly  worked. 

The  tempered  clay  is  then  dropped  into  the  augur  machine, 
which  is  essentially  a  closed  mixer  or  pug  mill  operating  under  pres- 
sure. A  heavy  shaft  with  a  screw  thread  or  worm  turns  in  a  heavy 
closed  cylinder,  open,  however,  on  top  at  the  rear  end  to  receive  the 


46  MANUFACTURE  OF  BRICK 

clay  and  on  its  axis  at  the  other  end  to  receive  the  mouthpiece  or  die 
as  an  outlet. 

The  action  of  the  worm  or  augur  gradually  moves  and  com- 
pacts the  tempered  clay  in  the  forward  end  of  the  cylinder  where  a 
gradual  reduction  in  cross  section  of  the  cylinder  further  increases 
the  compression  in  the  clay.  This  compacted  column  of  clay  as  it  is 
pushed  forward  by  the  steady  action  of  the  worm  is  changed  from 
circular  to  rectangular  form  by  the  mouthpiece,  finally  exuding  from 
the  die  as  a  continuous  column  of  clay  of  a  cross  section  similar  to 
the  brick  being  manufactured. 


Fig.    16— The    Dry    Pan. 

Since  the  clay  column  must  have  the  greatest  possible  density, 
it  follows  that  the  augur  must  be  built  very  heavy  and  strong  in  order 
to  withstand  the  extreme  pressures  caused  by  compacting  the  stiff 
clay.  In  this  machine  the  loose  granular,  moist  particles  of  clay  are 
transformed  into  a  dense,  compact,  plastic  column  of  uniform  rect- 
angular cross  section.  This  transformation  takes  place  in  the  for- 
ward part  of  the  cylinder,  especially  in  the  tapering  mouthpiece  and 
the  die.  The  design  of  the  shape  and  length  of  this  mouthpiece  rep- 
resents one  of  the  most  delicate  engineering  problems  in  connection 
with  brick  making.  The  shape  and  length  of  the  taper  depends  on 
the  clay,  some  clay  taking  a  reduction  in  cross  section  more  rapidly 
without  detriment  than  others,  and  on  the  relative  size  of  the 
cross  section  of  the  augur  barrel  and  the  die.  The  mouthpiece  taper 
can  best  be  determined  by  experiment  but  must  insure  a  clay  column 
of  absolute  uniformity  and  density  throughout.  The  reduction  in 
cross  section  must  be  gradual  but  too  long  a  taper  may  give  a  brick 
with  weak  corners. 

Let  us  consider  for  a  moment  what  takes  place  in  the  forward 
part  of  the  moulding  machine.  The  worm  compresses  the  clay  in  the 
front  part  of  the  cylinder  in  the  form  of  a  series  of  spiral  layers.  If 


MANUFACTURE  OF  BRICK 


47 


the  clay  has  not  been  properly  tempered,  these  layers  are  distinctly 
laminated,  but  even  where  there  may  appear  to  be  perfect  adhesion 
between  the  layers,  it  is  probable  that  there  is  some  slight  line  of 
demarcation  due  to  the  troweling  action  of  the  augur.  As  the  cylinder 


of  compacted  clay  enters  the  tapering  former,  these  layers  are  per- 
pendicular to  the  axis  of  the  cylinder.  In  being  pushed  through  this 
mouthpiece,  it  is  evident  and  has  been  demonstrated  by  experiment, 
that  the  central  portion  of  the  cylinder  travels  forward  faster  than 
the  outer  portion  both  on  account  of  the  reduction  in  section  and  the 
friction  on  the  sides.  The  original  verticle  layers  of  the  clay  cylinder 


48 


MANUFACTURE  OF  BRICK 


therefore  become  long  superimposed  cones  with  their  axis  lying  along 
the  horizontal  longitudinal  axis  of  the  clay  column  as  it  emerges 
from  the  die.  The  shape  and  length  of  these  cones  depend  on  the 
rapidity  with  which  the  clay  has  been  reduced  in  section  and  on  the 

plasticity  of  the  clay.  By 
changes  in  the  tapering  former 
they  can  be  made  to  take  any 
shape  desired.  It  is  probable 
also  that  the  particles  of  shale 
themselves  become  arranged 
with  their  longer  dimension 
parallel  to  the  longitudinal  axis 
of  the  clay  column  in  passing 
through  the  tapering  mouth- 
piece on  account  of  the  gradu- 
ally increasing  pressure,  the 
internal  friction  set  up  by  the 
reduction  in  section  and  the 
graduated  variation  in  speed  of 
travel.  It  will  be  shown  later 
that  while  the  burning  greatly 
improves  the  clay  structure,  it 
does  not  make  any  radical 
change  in  the  structure  itself. 

Vertical  Fiber  Paving  Brick 
are  so  named,  because  they  are 
formed  so  that  the  axes  of  the 
cones  and  the  elongated  clay 
particles  are  vertical  as  the 
brick  is  laid  in  the  street.  In 
this  position  the  brick  are  in  the 
most  favorable  condition  to  re- 
sist wear  and  advantage  is  taken 
of  the  internal  structure  of  the 
brick.  It  is  scarcely  correct  to 
say  that  a  vitrified  brick  is  fi- 
brous, but  the  term  Vertical 
Fiber  probably  describes  the 
condition  better  than  any  other. 
The  advantage  gained  by  so  lay- 
ing the  brick  that  the  internal 
structural  layers  are  vertical  is 
slight  compared  to  the  impor- 
tance of  the  other  steps  in  the 
process  of  manufacture,  but  it 
represents  an  additional  factor 

of  safety  in  the  pavement  and  illustrates  one  of  the  many  technical 

details  the  modern  paving  brick  manufacturer  is  constantly  adding. 

The  die  through  which  the  clay  is  forced  by  the  augur  ma- 

chine, is  a  part  of  the  former  and  is  rectangular  in  section,  the  longest 


ig  —  The  Parts  to  a  Die. 


MANUFACTURE  OF  BRICK 


49 


dimension  usually  corresponding  to  the  length  of  the  paving  blocks 
with  an  allowance  for  shrinkage  in  burning.  The  lining  of  the  die 
must  be  smooth,  true  to  shape  and  easily  renewable  as  the  wear  is 
very  great.  It  is  lubricated  with  water,  steam,  oil  or  even  electricity 


and  so  designed  that  all  parts  of  the  clay  column  in  passing  through 
it,  travel  at  approximately  the  same  rate  of  speed;  otherwise  the  cen- 
tral section  is  apt  to  travel  faster  than  the  edges  and  much  faster  than 
the  corners,  producing  ragged  edges  and  torn  corners.  The  augur 


50  MANUFACTURE  OF  BRICK 

machine '  and  die  must  produce  a  homogeneous  column  of  clay,  tho- 
roughly compressed  and  free  from  internal  strains  so  as  to  prevent 
subsequent  twisting,  laminations  and  cracking  during  drying.  The 
continuous  clay  column  as  it  leaves  the  die  is  pushed  by  the  force  be- 
hind it  over  a  moveable  belt  to  the  cutting  table. 

The  cutting  table  is  practically  at  the  same  level  as  the  bottom 
of  the  die  and  must  be  constructed  as  carefully  and  substantially  as 
a  machine  lathe.  In  one  form  of  machine  the  floor  of  the  table  is 
slotted  to  allow  the  passage  of  the  piano  wires,  which  cut  the  clay 
column  into  blocks  of  the  proper  thickness.  In  another  make  of  ma- 
chine the  column  is  pushed  through  stationery  vertical  wires.  The 
wires  should  be  as  thin  as  possible  and  must  be  kept  taut  and  clean 
so  as  not  to  tear  the  edges  of  the  cut  blocks.  The  repress  was  in- 
vented and  used  formerly  to  correct  the  defects  in  the  clay  structure 
due  to  faulty  augur  machines,  dies  and  cutting  tables. 


Fig.    20 — The    Repress. 

The  repress  consists  of  a  metal  box  with  an  open  top  of  the 
size  of  the  block  cut  from  the  clay  column,  set  on  a  strong  iron  frame 
and  with  a  plunger  the  size  of  the  box  opening  which  comes  down 
on  the  clay  block  in  the  box  with  a  steadily  increasing  pressure. 

The  box  or  repress  mould  is  so  shaped  that  round  corners, 
lugs  and  the  trade  name  of  the  brick  are  formed.  We  have  seen  that 
the  clay  column  as  it  emerges  from  the  die  has  a  definite  set  or 
structure.  After  being  cut  into  blocks,  if  these  blocks  could  be  re- 
pressed in  a  true  mould  with  pressure  exerted  in  the  same  manner  as 


MANUFACTURE  OF  BRICK  51 

in  the  augur  machine,  the  additional  compression  would  undoubtedly 
add  to  this  set,  but  any  change  in  the  shape  of  the  clay  blocks  or  dir- 
ection of  the  compressive  force  means  a  disruption  of  the  original 
form.  No  repressing  machine  has  been  designed  which  exerts  equal 
pressure  on  all  sides  of  the  clay  blocks  and  the  form  is  also  changed 
by  the  addition  of  lugs  and  round  corners.  The  press  box  must  be 
slightly  larger  than  the  cut  clay  block  it  is  made  to  receive  so  that 
the  block  can  be  dropped  in  easily,  hence  the  repress  compresses  the 
block  in  one  direction  but  expands  it  in  the  other  two  dimensions. 
Experiments  and  measurements  invariably  show  that  the  repress  in- 
creases the  cubical  volume  of  the  clay  block.  The  rounded  corners 
are  a  necessity  in  the  repressed  brick  as  it  would  be  impossible  to 
maintain  the  square  edges  in  the  mould.  They  also  add  to  the  appear- 
ance of  the  paving  brick  and  enable  it  to  show  a  lower  percentage 
of  loss  in  the  rattler.  All  tests  of  the  material  however,  seem  to 
show  that  a  well  made,  non-repressed  block  is  much  stronger  and 
freer  from  structural  defects  than  when  subjected  to  repressing.  Since 
the  development  of  brick  machines  and  automatic  wire  cutters  has 
made  possible  the  forming  of  a  high  grade  block,  the  wire  cut  product 
has  been  rapidly  displacing  the  repressed  block.  There  are  two 
methods  of  forming  the  clay  blocks  by  the  wire  cut  process. 

In  one  the  wires  of  the  cutter  are  guided  in  narrow  waved  and 
straight  slots  cut  in  steel  plates  placed  above  and  below  the  clay 
column  thus  forming  two  knobs  or  lugs  on  both  the  upper  and  lower 
edges  of  the  cut  block.  The  alternate  slots  are  straight  so  that  the 
lugs  are  formed  on  only  one  side  of  each  block.  On  account  of  the 
tilting  of  the  wires  in  passing  through  the  slot,  the  knobs  are  beveled, 
projecting  the  furthest  on  the  upper  and  lower  surfaces  of  the  block. 
This  form  of  block  is  known  as  the  Dunn  Wire-Cut-Lug  Paving  Block, 
and  this  form  of  wire  cutting  machine  is  patented  and  can  be  used  only 
by  manufacturers  licensed  by  the  patentee.  The  lugs  are  accurately 
formed  and  provide  uniform  spacing  of  the  blocks  in  the  street  while 
the  slightly  roughened  wire  cut  surface  forms  an  excellent  bond  with 
cement  grout  when  it  is  used  as  a  filler  for  the  joints  of  the  pave- 
ment. The  wearing  surface  of  the  brick  is,  however,  the  smooth  sur- 
face formed  by  the  die,  and  the  conical  clay  layers  are  horizontal  in- 
tead  of  vertical  as  laid  in  the  pavement.  Two  of  the  four  edges  of  the 
brick  exposed  to  wear  in  the  street  are  also  necessarily  slightly 
rounded  as  they  are  formed  on  the  clay  column  by  the  die.  The 
depth  of  the  brick  as  a  pavement  wearing  surface  can  only  be  varied 
in  the  wire-cut-lug  brick  by  a  change  in  the  die  or  mouthpiece  of  the 
forming  machine  and  on  account  of  the  difficulty  in  getting  a  uniform 
clay  structure  where  there  is  considerable  difference  in  the  two  di- 
mensions of  the  die,  a  thin  brick  of  standard  length,  if  desired,  is  not 
practical. 

In  the  other  form  of  wire  cut  paving  brick,  the  lugs  are  formed 
as  two  continuous  parallel  ridges  on  the  top  surface  of  the  clay  column 
by  corresponding  grooves  in  the  upper  face  of  the  die.  The  blocks  are 
then  cut  along  a  plane  surface  by  straight  taut  wires.  The  spacing 
of  the  wires  determines  the  depth  of  the  brick  and  the  die  remains 
for  all  depth  of  brick  the  same.  The  brick  as  set  in  the  pavement,  are 
turned  with  a  wire  cut  face  uppermost,  and  the  lugs  projecting  the 
same  distance  for  the  full  depth  of  the  block  provide  uniform  spacing 
for  the  filler.  This  form  of  wire  cut  brick,  the  Vertical  Fiber  Brick 


-:tv. 


MANUFACTURE  OF  BRICK  53 

Block,  has  been  shown  to  be  so  placed  in  the  street  as  to  take  ad- 
vantage of  the  internally  formed  structure  of  the  clay.  It  is  not  a 
patented  article  but  can  be  made  by  any  manufacturer  with  the  proper 
equipment.  It  can  be  made  any  depth  desired.  The  reticulated  wire 
cut  surface  is  not  slick,  affording  a  good  foothold  and,  when  a  bi- 
tuminous filler  is  used,  aids  in  retaining  a  carpet  of  bituminous  ma- 
terial on  the  surface.  All  four  edges  of  the  brick  surface  are  square 
making  a  uniform  width  of  joint  from  top  to  bottom  of  the  brick  on  all 
sides.  The  Vertical  Fibre  brick  can  also  be  so  piled  in  the  kiln  that 
all  kiln  marks  occur  on  the  sides,  leaving  the  bedding  and  wearing 
surface  free  from  kiln  marks  or  warps  and  thus  providing  a  brick, 
which  lays  much  smoother  than  other  forms  of  paving  brick.  The 
area  of  the  face  of  the  Vertical  Fiber  Paving  Block  exposed  to  wear 
is  usually  10  to  50%  greater  than  other  paving  brick  and  there  are 
consequently  fewer  brick  to  be  laid  to  the  square  yard  of  pavement  and 
fewer  joints  in  the  pavement.  While  a  number  of  engineers  con- 
tinue to  specify  the  old  repressed  brick  block,  the  wire  cut  product 
is  rapidly  gaining  jn  favor,  the  Dunn  Brick  in  the  Eastern  and  Central 
States  and  the  Vertical  Fiber  in  the  Central  Western  and  Southern 
States,  the  present  tendency  being  to  use  a  plain  wire  cut  brick  with- 
out lugs. 

To  continue  with  the  process  of  manufacture,  the  clay  blocks 
as  they  leave  the  repress  or  the  cutting  table  as  the  case  may  be, 
are  racked  on  small  cars  and  wheeled  to  the  drying  room.  Here  a 
large  portion  of  the  moisture  in  the  brick  is  removed  by  means  of 
circulating  steam,  warm  air  or  kiln  gases.  There  are  many  different 
forms  of  driers  depending  on  the  nature  of  the  clay  but  the  rate  of 
drying  must  be  under  careful  control  to  prevent  checking.  The  rate 
of  drying  can  be  partially  controlled  by  the  method  of  piling  the 
brick,  but  the  temperature  in  the  drier  must  also  be  carefully  regu- 
lated. There  is  seldom  less  than  fifteen  per  cent  of  water  in  tne  clay 
block  and  the  object  of  the  drying  is  to  remove  as  much  of  this  at  low 
temperatures  as  possible.  The  drying  requires  from  one  to  three  days 
and  the  brick  as  they  come  from  the  dryer  are  strong  enough  to  be 
piled  in  the  kiln. 

Kilns  are  classed  as  single  or  intermittent,  semi-continuous, 
and  continuous,  and  each  class  is  divided  according  to  the  path  the 
heated  gases  from  the  fires  take  as  up-draught,  down-draught  or 
horizontal  draught.  The  majority  of  kilns  used  for  burning  paving 
blocks  in  the  United  States  are  of  the  down-draught  intermittent  type. 
Many  plants  have  some  form  of  continuous  kiln,  and  this  type  has  been 
growing  in  favor.  Continuous  kilns  are  especially  suitable  and  eco- 
nomical for  large  plants  which  operate  throughout  the  year  and  have 
a  large  output.  When  properly  constructed  and  run,  the  percentage 
of  No.  1  Pavers  is  equal  to  that  obtained  from  the  down-draught  in- 
termittent kiln  and  a  considerable  saving  in  fuel  is  made.  The  kilns 
must  be  very  substantially  constructed  to  resist  the  extreme  heat  and 
the  expansion  and  contraction  due  to  the  variations  in  temperature. 
Adequate  provision  must  be  made  to  control  the  temperature  in  all 
parts  of  the  kiln  as  this  is  the  only  way  to  secure  a  uniformly  good 
product.  The  single  down-draught  kiln  is  rectangular  or  circular  in 
shape  with  a  number  of  bags  or  pockets  on  the  inside  along  each  of  the 
side  walls  for  the  fires.  The  floor  of  the  kiln  is  sometimes  perforated 
throughout  and  always  has  numerous  openings  leading  to  flues  which 


MANUFACTURE  OF  BRICK 


the  floor  to  the 


The  roof  is  a  tight,  flat,  brick 


•reft  -^. 

h  Ion  -.-;-.  ia 
the  fire 
where  it 

Aeaee  h  Dhi 


Baffle  «aHsm 

the  sides  of  the  kfln  to  the  top 
the  brick  to  the 


-:   -.-•:    ---:-    ;..-. 


OB  eace  IS  to  3* 


(3)  the  vitrifyiag 


ashrick  wffl  he 


56  MANUFACTURE  OF  BRICK 

danger  of  overheating  and  warping  the  blocks.  It  should  be  under- 
stood that  the  dictionary  meaning  of  vitrification, — "to  render  glassy" 
— does  not  strictly  apply  to  clay  products.  A  glassy  brick  would  be 
too  smooth  and  fragile  for  paving  purposes.  As  applied  in  a  com- 
mercial sense  to  clay  products,  the  term  "vitrified"  means  that  "a 
chemical  action  has  taken  place  so  that  the  clay  particles  have 
coalesced  and  become  fused  by  the  action  of  heat,  forming  a  new 
homogeneous  whole,  but  not  that  fusion  has  been  made  complete  by 
bringing  the  entire  mass  to  a  semi-fluid  state."  As  soon  as  the  great- 
est number  of  brick  possible  in  the  kiln  have  been  heated  through  to 
a  temperature  short  of  melting,  the  burning  may  be  said  to  have  been 
completed,  the  fires  are  drawn,  all  openings  and  dampers  in  the  kiln 
closed  and  the  brick  annealed  by  slow  cooling.  The  hot  gases  from 
cooling  kilns  are  frequently  used  by  special  flues  in  the  drier.  Slow 
cooling  of  the  brick  is  the  secret  of  toughness.  Drafts  of  cool  air  ad- 
mitted through  the  fires  during  burning  and  through  openings  in  the 
kiln  during  the  first  stages  of  cooling  will  chill  the  brick  or  cause  air 
checking.  There  is  always  a  tendency  to  hurry  the  annealing  process, 
but  the  length  of  time  allowed  for  cooling  depends  a  great  deal  on  the 
material,  some  clays  only  requiring  2  or  3  days  while  others  take 
from  5  to  10  days. 

In  a  properly  burned  kiln  after  it  is  opened,  it  is  found  that  the 
top  course  is  extremely  hard,  glassy  and  more  or  less  air  checked. 
Beneath  this  and  down  to  within  2  to  10  courses  from  the  bottom  are 
the  No.  1  pavers,  sound,  vitrified,  strong,  hard  and  tough.  Beneath 
these  are  the  hard  burned  "builders."  The  actual  percentage  of  yield 
of  good  quality  paving  brick  is  subject  to  so  many  variables,  that  it 
is  difficult  to  forecast.  The  temperatures  in  the  kilns  were  formerly 
determined  by  the  judgment  of  the  burners  and  the  amount  of  settle- 
ment as  measured  at  intervals  through  openings  in  the  top  of  the 
kiln.  This  was  indefinite  and  unsatisfactory  and  although  the  amount 
of  settlement  still  remains  the  key  to  proper  firing  it  has  been  sup- 
plemented by  using  Seger  Cones,  specially  prepared  clay  cones  placed 
in  the  kiln  which  melt  at  a  specific  temperature,  or  by  observations 
through  peepholes  in  different  parts  of  the  kiln  by  means  of  a  pyro- 
scope,  an  instrument  for  measuring  high  temperatures  by  radiation. 
Some  of  the  more  modern  plants  have  installed  pyrometers  in  different 
parts  of  the  kilns  which  electrically  record  temperatures  throughout 
the  burning  and  cooling  process  insuring  accurate  control  at  all  times. 

The  engineer,  however,  is  seldom  able  to  inspect  the  entire 
process  of  manufacture  of  the  brick  he  expects  to  use  in  a  pavement 
and  while  a  visit  to  a  plant,  which  is  well  equipped  with  modern 
machinery  and  where  up-to-date  methods  and  careful  supervision  are 
in-  evidence,  may  greatly  increase  his  confidence  in  the  product,  his 
problem  is  usually  one  of  determining  the  suitableness  of  material 
as  it  is  loaded  in  cars  or  delivered  on  the  street.  The  qualities  of 
good  paving  brick  are  the  same  as  for  any  other  paving  material- 
hardness,  toughness  and  ability  to  resist  water  and  frost.  Tests  to 
determine  these  qualities  have  been  evolved  and  standardized  through 
years  of  experimenting.  In  the  early  days  of  brick  pavement,  tests 
for  absorption,  crushing  strength,  specific  gravity,  modulus  of  rupture 
and  the  like  were  required.  The  absorption  and  specific  gravity 
tests  were  supposed  to  indicate  the  density  and  degree  of  vitrifica- 
tion, but  the  hardest  burned  brick  which  showed  the  lowest  on  these 
tests  were  frequently  too  brittle  to  stand  traffic.  It  was  found  also 


MANUFACTURE  OF  BRICK 


57 


that  equally  good  brick  from  different  localities  varied  in  specific 
gravity  and  amount  of  absorption  within  considerable  limits  so  that 
any  attempt  to  fix  limits  for  these  tests  would  either  eliminate  all 
but  one  or  two  manufacturers  or  pass  No.  2  brick  from  plants  which 
naturally  gave  low  absorption  and  high  specific  gravity  tests. 

Low  absorption  of  paving  brick  is  not  essential  to  durability. 
Hard  burned  building  brick,  which  absorb  two  to  three  times  the 
amount  of  water  a  vitrified  paving  brick  will  take  up,  are  unaffected 
by  water  or  frost.  About  the  same  can  be  said  of  the  tests  for  crush- 
ing and  breaking  strength;  within  considerable  limits  they  depend  on 


Fig.  23 — The  Standard  Rattler. 

the  kind  of  clay  used  in  the  brick  and  are  riot  indicative  of  a  suitable 
wearing  surface.  In  order  to  duplicate  conditions  of  wear  in  the 
streets,  the  so-called  "rattler  test"  was  invented  and  adopted  as 
standard  in  1901  by  the  National  Paving  Brick  Manufacturers  Asso- 
ciation. It  was  based  on  a  long  series  of  tests  made  on  brick  from 
old  pavements  and  from  plants  throughout  the  country.  The  first 
machine,  however,  proved  to  be  incapable  of  maintaining  uniform  con- 
ditions in  successive  tests  and  in  1911  the  details  of  the  construc- 
tion of  the  rattler  barrel  were  changed  and  round  shot  substituted  for 
rectangular  shot  as  the  abrasive  charge.*  The  rattler  test  con- 
sists briefly  of  measuring  the  wear  on  a  sample  of  ten  paving  brick 
when  tumbled  loosely  with  225  pounds  of  iron  spheres  1%  inches 
in  diameter  and  75  pounds  of  iron  spheres  3%  inches  in  diameter  in 
an  iron  chamber  making  1,800  revolutions  in  approximately  one 

*See  Page  106  for  complete  description  of  the  rattler  and  method  of 
making  the  test. 


58  MANUFACTURE  OF  BRICK 

hour.  The  size  and  construction  of  the  rattler  barrel,  the  com- 
position of  the  iron  composing  the  abrasive  charge,  the  speed  of 
the  rattler  and  all  other  details  are  carefully  fixed  or  limited 
so  that  tests  may  be  comparable.  The  standard  test  for  instance 
requires  that  the  speed  shall  not  be  less  than  29.5  nor  more  than 
30.'5  revolutions  per  minute.  A  slight  variation  in  speed  beyond 
these  limits  may  make  a  more  severe  test,  while  a  greatly  increased 
speed  might  be  less  severe.  The  brick  selected  for  the  test  should 
always  be  dried  if  necessary  as  water  in  the  brick  not  only  affects  the 
computation  of  loss  but  may  also  actually  decrease  or  increase 
the  amount  of  loss  sustained.  In  other  words,  every  effort  should 
be  made  to  carry  out  each  test  in  exact  conformity  with  the  stan- 
ardized  requirements  so  that  tests  made  on  different  shipments  or  by 
different  manufacturers  or  for  different  streets,  may  be  comparable. 

The  rattler  test  is  intended  to  duplicate  as  nearly  as  possible 
the  conditions  met  in  a  street  pavement,  the  large  spheres  giving  the 
sharp  hard  blows  and  the  small  spheres  the  grinding,  polishing  action 
received  from  street  traffic.  In  this  way  the  rattler  tests  not  only 
the  toughness  and  homogenity  of  the  brick  but  also  the  hardness, 
strength  and  durability.  It  determines  better  than  any  other  test 
the  suitableness  of  brick  for  paving  purposes. 

The  amount  of  wear  on  the  sample  of  brick  is  determined  by 
weighing  them  before  the  test  and  after  the  1,800  revolutions  in  the 
rattler.  The  difference  in  weight  is  figured  as  a  percentage  of  the 
original  weight.  The  engineer  usually  fixes  the  maximum  permlss- 
able  percentage  of  loss  and  requires  all  brick  furnished  by  the  con- 
tractor to  come  within  this  limit. 

In  fixing  a  limited  abrasion  loss,  the  engineer  must  keep  in 
mind  the  size  and  shape  of  brick  he  proposes  to  use,  and  the  charac- 
ter of  traffic  the  street  or  road  to  be  paved,  will  receive.  It  is  evi- 
dent that  the  edges  of  the  brick  are  the  least  able  to  withstand  the 
punishment  to  which  they  are  subjected  in  the  rattler,  and  therefore 
a  square  edged  brick  like  the  Vertical  Fiber  or  wire-cut  brick  will 
show  a  greater  loss  for  the  same  quality  of  brick  than  a  block  the 
edges  of  which  are  rounded  by  the  repress.  Because  of  the  greater- 
ratio  of  edges  to  weight,  a  small  sized  brick  will  show  a  larger  per- 
centage of  wear  than  a  large  sized  brick.  Allowance  should  always 
be  made  for  these  conditions  or  the  engineer  may  find  himself  in  the 
uncomfortable  position  of  having  specified  a  much  higher  grade  of 
brick  material  for  an  outlying  residence  street  where  he  uses  two 
and  one  half  inch  depth  Vertical  Fiber  than  he  must  accept  for  a 
four  inch  depth  block  on  a  heavy  traffic  downtown  street.  The  quality 
of  the  brick  which  will  be  acceptable  should  be  decided  after  a  study 
of  the  nature  and  probable  amount  of  traffic  which  the  pavement 
will  receive  in  the  same  way  that  the  depth  of  foundation  and  other 
features  of  the  design  of  a  pavement  are  determined.  A  failure  to 
take  account  of  all  these  conditions  is  nothing  less  than  an  economic 
blunder. 

For  the  heaviest  traffic  streets  in  cities,  a  round  cornered  brick 
block,  which  shows  an  abrasion  loss  by  the  standard  rattler  test  of 
20  or  21  per  cent  or  less  will  be  entirely  suitable.  If  a  square  cor- 
nered wire-cut-lug  block  four  inches  in  depth  is  used,  an  additional  al- 
lowance of  two  per  cent  should  be  made  and  the  limits  fixed  at  22  to 


MANUFACTURE  OF  BRICK  59 

23  per  cent  loss.  For  retail  business  streets,  an  allowable  loss  of  22 
and  24  per  cent  for  the  repressed  and  square  edged  block  respectively 
will  prove  economical.  Where  three  inch  Vertical  Fiber  brick  are 
used  on  the  business  streets  in  towns  or  small  cities  a  limit  of  24 
to  26  per  cent  gives  an  excellent  quality  of  brick  material,  while  on 
country  roads  or  light  traffic  streets  in  towns  a  maximum  limit  of  25 
or  26  per  cent  will  serve.  On  account  of  its  small  size  and  the  extra 
loss  on  account  of  an  occassional  broken  brick  in  the  rattler,  a  two 
and  half  inch  depth  Vertical  Fiber  brick  requires  an  allowance  of 
2.6  to  28  per  cent  to  insure  the  best  grade  of  material,  while  a  permiss- 
able  loss  of  as  much  as  28  to  32  per  cent  is  not  out  of  the  way  for 
certain  conditions  of  traffic  and  location. 

The  tendency  of  engineers  has  been  to  consider  the  brick  show- 
ing the  lowest  per  cent  of  loss  in  the  rattler  test  as  the  best  brick. 
It  is  undoubtedly  the  hardest  and  toughest  material  but  it  is  the 
opinion  of  some  engineers  that  extreme  hardness  and  toughness  are 
not  neccessarily  desirable  for  a  pavement.  Street  traffic  will  cause 
practically  no  wear  on  a  brick  showing  as  low  as  16  per  cent  in  the 
rattler  and  the  pavement  will  deteriorate  only  by  the  edges  of  the 
brick  breaking  off  through  failure  of  the  joint  filler,  uneveness  in  lay- 
ing or  sunken  places.  It  is  conceivable  that  a  softer  brick,  which 
would  wear  down  somewhat  under  traffic,  would  produce  a  smoother 
appearance,  and  preserve  an  unimpaired  surface  longer  than  would  a 
very  hard  brick. 

Some  slight  abrasive  wear  is  desirable  on  all  kinds  of  pave- 
ments in  order  to  keep  them  smooth  and  uniform.  The  harder  the 
brick  material,  moreover,  the  greater  the  modulus  of  elasticity  and 
therefore  the  greater  the  confined  stresses  in  a  cement  grouted  pave- 
ment slab  caused  by  expansion  and  contraction. 

It  is  apparent  that  the  most  desirable  quality  for  a  shipment  of 
paving  brick  to  possess  is  absolute  uniformity.  It  has  been  shown  that 
even  under  the  most  favorable  conditions  of  manufacture,  brick  will 
vary  slightly  in  quality  due  to  variations  in  the  clay,  methods  of 
handling,  and  degrees  of  heat  in  different  parts  of  the  kiln.  Some 
engineers  are  fixing  minimum  as  well  as  maximum  limits  to  the  rat- 
tler loss,  while  others  have  gone  so  far  as  to  mark  and  weigh  each 
brick  before  testing  and  requiring  that  the  loss  of  any  one  brick  shall 
not  vary  more  than  i3  points,  for  example,  from  the  average  loss  of 
the  whole  charge.  A  severe  requirement  of  this  kind  does  not  ap- 
pear to  be  necessary.  It  is  difficult  to  enforce,  calls  for  greater 
refinement  than  the  material  or  method  of  testing  warrants,  and 
would  probably  raise  the  price  of  the  material  out  of  proportion  to 
any  benefits  received. 

The  specifications  for  a  street  subjected  to  very  severe  traffic 
conditions,  might  call  for  brick  block  not  exceeding  say  22  per  cent 
abrasion  loss  and  no  single  rattler  test  to  vary  more  than  iy2  or  2 
points  above  or  below  a  figure  fixed  by  the  manufacture  as  the  aver- 
age of  the  brick  passing  a  22  per  cent  test  he  proposes  to  furnish. 
This  would  insure  great  uniformity  in  the  material,  if  the  samples 
were  selected  and  the  tests  made  as  prescribed  in  the  standardized 
method  of  conducting  rattler  tests.  (See  pages  106  to  110.) 

In  all  cases  a  much  better  selection  can  be  obtained  if  the  in- 
spector for  the  engineer  sorts  and  tests  the  brick  at  the  manufacturing 


60  MANUFACTURE  OF  BRICK 

plant.  By  this  method  any  differences  of  opinion  regarding  the  in- 
terpretation of  the  specifications  can  be  adjusted  before  shipment  be- 
gins, delays  are  avoided  and  the  interests  of  both  purchaser  and 
manufacturer  are  protected.  By  testing  the  brick  by  courses  in  the 
kiln  and  loading  directly  into  cars,  a  very  uniformly  burned  product 
may  be  secured,  and  a  competent  brick  inspector  can  make  his  selec- 
tions to  much  better  advantage  at  the  plant  than  by  sampling  a  car- 
load after  it  arrives  on  the  work.  Plant  inspection  and  acceptance  is 
encouraged  by  the  manufacturers  and  should  be  insisted  upon  by  the 
engineers  for  all  work  of  any  magnitude. 

Considerable  space  has  been  devoted  to  the  rattler  test,  be- 
cause it  has  taken  the  place  of  all  other  tests  for  determining  the 
density,  strength,  hardness  and  toughness  of  paving  brick.  It  has 
been  shown  in  the  description  of  the  method  of  making  brick  that  the 
defects  likely  to  occur  are  of  such  a  nature  that  they  will  be  apparent 
on  visual  inspection  or  will  show  up  by  excessive  wear  in  the  rat- 
tler. Visual  inspection  will  disclose  the  misshapen,  warped,  cracked, 
and  off-size  brick,  that  is,  brick  which  will  not  lay  evenly  in  the  street, 
but  must  not  be  depended  upon  to  pass  on  the  quality  of  the  brick  ma- 
terial itself,  especially  if  brick  from  different  plants  are  to  be  select- 
ed. The  rattler  is  best  able  to  discover  the  soft,  brittle  or  weak 
brick  material.  A  specification,  which  limits  the  variation  in  width 
and  depth  of  brick  so  that  they  may  be  bedded  evenly  and  with  uni- 
form width  of  joint,  rejects  the  badly  chipped,  broken  kiln  marked 
and  warped  brick  which  would  make  a  rough  and  uneven  surface, 
and  throws  out  soft,  brittle  or  weak  brick  by  a  suitable  rattler  test 
requirement,  will  make  certain,  when  intelligently  enforced,  the  re- 
ceipt of  a  satisfactory,  durable,  well  manufactured,  lasting  brick  pav- 
ing material. 


CHAPTER  V 

LAYING  THE  BRICK 


GHE  PLACING  OF  THE  BRICK  to  form  the  wearing  surface  re- 
quires the  same  care  and  intelligent  supervision  that  has  been 
urged  in  the  construction  of  the  foundation  and  the  selec- 
tion of  the  brick.  (Like  the  other  parts  of  the  pavement,  the 
wearing  surface  should  be  designed  and  constructed  of  a  type 
most  suitable  for  the  street  or  road  on  which  it  is  laid.  There  are 
a  number  of  different  methods  of  building  a  pavement  surface  of 
brick,  each  method  having  some  advantages  not  possessed  by  the 
others  from  the  point  of  view  either  of  cost  or  service;  and  that  type 
should  be  selected  which  most  nearly  satisfies  the  conditions  on  the 
street  to  be  paved.  Good,  serviceable,  and  durable  brick  pavements, 
have  been  built  in  a  number  of  different  ways,  and  the  type  to  be 
selected  is  therefore  no  more  important  than  seeing  that  the  work- 
manship and  material  in  the  wearing  surface  are  of  the  best  quality. 
Until  recent  years  bricks  have  always  been  laid  on  a  layer  of 
sand;  before  the  days  of  concrete,  the  sand  was  laid  three  or  more 
inches  thick  and  formed  the  only  foundation.  After  concrete  came 
into  use,  the  sand  was  still  used  to  bed  the  brick  and  was  spread 
over  the  foundation  sometimes  as  much  as  three  inches  in  depth  and 
the  brick  tamped  into  this.  With  further  developments  in  concrete 
mixing  machinery,  steam  rollers,  better  brick,  and  a  better  knowledge 
of  the  function  of  the  sand  layer,  its  depth  has  been  gradually  re- 
duced to  a  point  where  it  is  just  sufficient  to  level  up  slight  de- 
pressions in  the  foundation  and  compensate  for  slight  variations  in 
the  depth  of  individual  brick.  In  fact  a  committee  of  the  American 
Society  of  Civil  Engineers  recently  recommended  that  enough  care 
be  used  in  obtaining  a  true  surface  to  the  concrete  base  so  that  the 
sand  layer  could  be  reduced  to  not  less  than  one  half  nor  more  than  one 
inch  in  depth.  It  is  recognized  that  a  thick  layer  of  loose,  mobile 
material  under  the  brick  is  the  cause  of  numerous  defects  in  old 
brick  surfaces.  Great  stress  is  often  laid  on  the  supposition  that  the 
sand  layer  forms  a  cushion  for  the  brick,  protecting  them  from  the 
blows  of  traffic.  It  has  been  shown  by  experiment,  however,  that  a 
layer  of  sand,  which  is  well  compacted  and  confined  has  but  little 
more  resiliency  than  the  concrete  foundation  under  it.  Resiliency  to 
be  of  any  advantage  must  be  of  uniform  amount  throughout  the  total 
area  and  this  can  only  be  obtained  in  a  sand  layer  by  thoroughly  com- 
pacting it.  The  term  sand  cushion  is  a  misnomer  and  sand  bed  or 
bedding  course  should  be  used  for  preciseness.  The  chief  function  of 
the  sand  layer  is  to  provide  an  adjustable  bedding  course  between 
the  solid  concrete  and  brick  so  that  each  individual  brick  will  have  a 
firm,  uniform  bearing  throughout  its  bedded  surface.  Any  load  or 
blow  coming  upon  the  brick  will  then  be  distributed  over  the  entire 
bearing  surface  and  eccentric  loads  will  not  cause  the  brick  to  tip 
or  deflect  if  the  bed  remains  firm.  It  is  evident  that  to  perform  this 
function  properly,  especially  where  the  brick  are  later  bonded  together 
in  one  solid  slab  by  a  cement  grout  filler,  the  sand  layer  should  not 
change  in  volume,  move  or  shift  after  the  brick  have  once  been  firmly 
bedded.  Now  the  volume  of  sand  increases  with  its  moisture  con- 
tent, and  sand  as  spread  on  the  foundation  is  frequently  moist  or  dry 


LAYING  THE  BRICK 

9* 

in  spots.     This  ma.es  it  pracf  ally 

sand  layer  so  that  parts  of  it  at  le^\  Jed  and  it  has  had  a  chance  to 

volume  after  the  pavement  «  comtfe  ted  an         ^  ^^  ^ 

dry  out.     The  dry  sand  is  also  ha  ™e  to  of  the  pavement    at 

sition  by  the  vibration  of  traffic^    At  tn  ^  ^^  points  wh 


cracks  in  the  curb  or 
it  is  not  confined,  the 
water  should  get 


^  ^^  points  wh 

or  shift  out  of  place,  and  if 
sand  may  be  washed  out.     In 
it  is  also  difficult  to  replace  the 
Curbed  for  several  feet  each 


Fig 


24-Preparing  the  Bedding  Course. 


M. 


64 


LAYING  THE  BRICK 


brick  and  the  concrete  foundation,  but  after  the  brick  have  been 
properly  bedded  and  the  cement-sand  cushion,  as  it  is  called,  sets, 
there  is  no  danger  of  its  shifting,  shrinking  or  moving.  Wherever 
it  has  been  used  it  has  proved  very  satisfactory.  Since  the  bedding 
course  does  not  shrink  away  from  the  brick,  hollow  spots  do  not 
develop  and  consequently  the  rumbling  noise  of  cement-grouted  brick 
is  almost  entirely  eliminated.  As  the  mixture  is  spread  dry,  it  forms 
a  porous,  granular  course  similar  to  the  ordinary  sand  layer  but  with 
enough  cement  in  it  to  hold  the  sand  grains  in  place.  The  cement 
in  the  cement-sand  bed  does  not  come  into  play  until  after  the  brick 
are  laid  and  rolled,  so  that  the  method  of  placing  it  and  laying  the 
brick  is  the  same  as  where  the  plain  sand  bed  is  used. 

The  sand  for  both  the  plain  sand  and  cement-sand  beds  should 
be  medium  coarse,  fairly  clean,  well  graded  and  sharp,  and  free  from 
any  particles  over  one  quarter  of  an  inch  in  diameter.  A  loamy, 
round  grained  sand  will  roll  up  between  the  joints  in  the  brick,  while 
with  a  fine  silt  sand  it  is  impossible  to  roll  the  brick  to  an  even 
surface. 


oooo       oooo 
oooo       oooo 


Fig.    26 — Turning-  Brick    to   Fit   Next   to   Manhole. 

The  sand  or  the  dry  mixture  of  cement  and  sand  should  be 
spread  with  shovels  to  an  approximately  uniform  depth  over  the 
smooth  concrete  base  and  struck  off  with  a  templet  similar  to  the 
one  used  for  striking  the  concrete  foundation.  The  ends  of  the  tem- 
plet rest  on  the  side  forms  or  on  wood  guide  strips  one  half  inch  thick 
placed  on  the  concrete  base  next  to  the  curb  and  brought  to  a  true 
grade  and  proper  height  by  bedding  in  a  little  sand.  Where  plain 
sand  is  used  the  templet  is  frequently  drawn  on  double  guides  which 
raise  it  a  half  inch  above  the  intended  final  surface  of  the  bedding 
course.  The  sand  is  then  rolled  with  a  heavy,  long  handled  hand- 
roller,  depressions  filled,  and  the  rolling  continued  until  a  true,  uni- 
formly compacted  surface  is  secured.  The  templet  is  again  drawn 
over  the  sand,  this  time  with  the  upper  guide  strips  removed,  if  double 


LAYING  THE  BRICK 


65 


guides  are  used,  leaving  the  sand  layer  ready  to  receive  the  brick 
and  true  to  grade  and  crown.  The  brick  are  then  laid  directly  on 
this  bedding  course. 

The  brick  are  laid  from  curb  to  curb  in  straight  courses  and  at 
right  angles  to  the  curb  with  the  lug  sides  all  in  the  same  direction. 
Each  alternate  course  is  started  with  a  half  brick  so  that  the  end 
joints  between  courses  of  brick  are  broken,  and  nothing  but  whole 
brick  are  used  except  at  the  ends  of  the  courses.  The  cutting  of 
closure  brick  must  be  carefully  done  and  no  pieces  of  brick  less  than 
two  inches  long  should  be  used,  a  part  being  cut  off  of  the  adjoining 
whole  brick  if  the  closure  space  is  less  than  two  inches.  In  cutting 


Fig.    27 — Heringbone    Intersection. 

around  manholes  or  valve  boxes,  care  must  be  taken  to  avoid  slivers 
or  small  pieces  of  brick  which  will  weaken  the  surface.  The  method 
shown  in  the  sketch  of  turning  two  or  three  brick  against  the  man- 
hole cover  lengthwise  of  the  street  is  recommended.  The  brick  should 
be  laid  so  that  the  lugs  of  the  brick  on  one  course  will  touch  the  brick 
in  the  adjoining  course  and  the  joints  between  the  ends  of  the  brick 
should  be  close  and  not  exceed  one  eighth  of  an  inch.  Frequently  one 


66 


LAYING  THE  BRICK 


or  more  courses  of  brick  next  the  curb  are  laid  lengthwise  of  the 
street  and  parallel  to  the  curb  but  there  is  not  much  advantage  in 
this  arrangement  and  on  narrow  roadways  where  traffic  is  crowded 
close  to  the  curb  the  continuous  longitudinal  joints  may  even  be 
detrimental.  At  intersections  where  the  cross  street  carries  little  or 
no  traffic  the  right-angled  courses  of  brick  may  be  carried  across  the 
intersection.  It  is  customary  and  better  practise  however  to  lay  the 
brick  so  that  the  wheels  of  the  vehicles  crossing  the  intersection  or 
those  turning  any  of  the  corners  will  not  have  an  opportunity  to  run 


Fig-.  28 Double  Diagonal  Intersection. 


in  an  unbroken  joint.  The  double  diagonal  method  of  laying  the  in- 
tersections is  probably  the  best  method  of  accomplishing  this  although 
some  prefer  the  herringbone  style  both  of  which  are  shown  in  the 
accompanying  diagrams. 

Care  must  be  exercised  in  handling  the  brick  both  from  the  car 
to  the  street  and  from  the  piles  to  the  bricklayers,  so  that  they  will 
not  become  damaged  by  chipping.  A  sharp  hard  blow  on  the  corner  or 
edge  will  chip  the  best  brick.  The  brick  should  be  carefully  handled 


LAYING  THE  BRICK 


67 


in  loading  and  unloading  and  should  not  be  thrown  or  dumped  into 
piles.  They  should  be  carried  to  the  brick  layers  on  pallets,  by 
clamps  or  on  conveyors  and  not  thrown  into  barrows  and  dumped  on 
the  pavement.  This  not  only  prevents  the  brick  from  being  chipped 


Fig-.   29 — Vertical  Fiber  Brick  Pavement,  Wichita,  Kas.,  Viaduct. 
Rolled  and  Culled.     Ready  for  Filler. 

but  avoids  disturbing  the  bricks  already  laid  and  increases  the  ef- 
ficiency of  the  bricklayers  by  placing  the  brick  so  that  they  may  be 
laid  with  the  least  effort.  The  brick  setters  stand  on  the  surface 
already  laid  and  place  each  brick  squarely  on  the  bedding  course 


68  LAYING  THE  BRICK 

without  disturbing  it  in  any  way.  This  requires  some  experience  and 
more  skill  than  may  be  evident  at  first  sight.  If  an  edge  or  end  of  a 
brick  is  placed  on  the  sand  layer  first,  the  sand  is  disturbed  and  the 
brick  dees  not  get  an  even  bed.  Shoving  or  driving  the  brick  into 
place  after  they  have  been  laid  is  apt  to  push  the  sand  up  between 
the  brick  and  settle  one  end  or  side  of  the  brick  below  the  general 
level.  The  brick  are  placed  in  close  contact,  in  straight  rows  and 
closures  are  made  immediately  following  the  laying  so  that  the  pave- 
ment may  be  rolled  and  the  joints  filled  without  delay.  The  brick 
should  first  be  rolled  with  a  light  roller  and  then  with  a  3  to  5  ton 
steam  roller.  A  horse  roller  ought  not  to  be  allowed.  The  object 
of  the  rolling  is  to  bed  each  brick  firmly  in  the  bedding  course  and 
to  bring  the  upper  surface  to  the  same  uniform  level.  The  light  roller 
gives  the  brick  a  slight  set  in  the  sand  so  that  the  first  passage  of  the 
heavier  roller  will  not  have  a  tendency  to  tilt  or  cause  them  to  creep. 
In  order  not  to  cause  the  sand  to  shift  under  the  bricks  during  the 
rolling,  the  pavement  is  first  rolled  longitudinally  beginning  on  one 
side  and  working  toward  the  center,  then  crossing  to  the  opposite 
gutter  and  working  toward  the  center,  each  part  of  the  pavement  re- 
ceiving a  passage  of  the  roller  going  both  backwards  and  forwards. 
The  brick  are  further  worked  down  to  a  uniform  bearing  and  level,  by 
rolling  the  pavement  in  both  diagonal  directions.  Places  inaccessable 
to  the  roller  are  tamped  with  a  heavy  ram  or  tamp,  striking  a  short 
piece  of  plank  moved  over  the  surface.  During  the  rolling,  the  brick 
which  have  been  broken  or  chipped  by  the  roller  are  removed  or  turned 
and  any  depressions  or  humps  which  will  not  roll  out  are  corrected  by 
removing  the  brick  and  readjusting  the  bedding  course.  When  the 
sand  layer  has  been  properly  prepared  and  the  rolling  thoroughly 
done,  the  resulting  surface  should  be  true  to  grade  and  crown,  even 
in  appearance,  and  with  each  brick  uniformly  and  solidly  bedded  so 
that  it  will  not  rock  or  tilt  when  it  is  stepped  on.  The  smoother  the 
surface,  the  better  and  more  durable  is  the  pavement.  It  is  very 
important  that  this  portion  of  the  work  be  carefully  inspected  and 
that  no  joint  filler  is  allowed  to  be  placed  until  a  satisfactory  surface 
is  secured.  It  is  frequently  required  that  the  surface  of  the  pave- 
ment be  tested  with  a  ten  foot  straight  edge  laid  longitudinally  and 
all  inequalities  exceeding  one  quarter  of  an  inch  be  corrected  before 
filling  the  joints.  If  cement  has  been  mixed  with  the  sand  in  the 
bedding  course,  the  surface  of  the  brick  should  be  thoroughly  sprinkled 
before  the  joint  filler  is  placed  in  order  to  add  enough  water  to  set 
the  cement. 

Three  forms  of  joint  filler  for  brick  pavements  have  been  in 
common  use:  sand,  Portland  Cement,  and  a  Bituminous  Cement  of  tar 
or  asphalt.  Sand  filler  was  used  on  nearly  all  the  early  brick 
streets,  hot  sand  being  swept  back  and  forth  over  the  pavement  sur- 
face until  all  the  joints  were  filled,  leaving  a  surplus  of  sand  on  the 
pavement  to  pack  into  the  joints  under  traffic.  About  the  only  thing 
to  recommend  a  sand  filler  is  its  cheapness.  It  does  not  furnish  a 
waterproof  surface  nor  protect  the  edges  of  the  brick  from  chip- 
ping. It  washes  out  of  the  top  of  the  joints  and  causes  a  dirty,  noisy 
pavement. 

On  a  large  majority  of  brick  pavements  in  the  past  fifteen  years 
Portland  Cement  and  sand,  mixed  with  water  to  a  thin  grout,  has  been 
used.  In  many  districts  cement  grout  is  the  only  filler  used,  and  it 


LAYING  THE  BRICK 


has  proven  very  satisfactory,  when  properly  handled.  Where  a  plain 
sand  bedding  course  for  the  brick  and  cement  grout  for  the  joints 
are  used,  care  must  be  taken  that  the  bedding  sand  does  not  roll 
up  between  the  brick  more  than  a  quarter  or  three  eighths  of  an  inch. 
If  the  bottom  of  the  joint  is  filled  with  sand,  the  homogeneity  of  the 


Fig.    30 — Filling-    the    Joints    with    Portland    Cement    Grout. 

joint  filler  is  destroyed,  and  a  failure  of  the  grout  may  result.  The 
sand  used  for  the  grout  should  be  clean,  sharp  and  medium  coarse ; 
fine  round  grained  sand  has  no  place  in  any  pavement.  The  sand 
and  cement  are  usually  mixed  in  equal  parts  and  in  small  batches 
but  proportions  as  lean  as  one  part  cement  to  two  parts  sand  have 
been  used,  Where  a  small  mixing  machine  is  not  available,  it  is 


70  LAYING  THE  BRICK 

recommended  that  the  batches  of  grout  be  mixed  in  small,  tight, 
rectangular  boxes  supported  on  four  legs  of  unequal  length  so  that 
the  floor  of  the  box  is  inclined  and  one  corner  is  lower  than  all  the 
rest.  The  sand  and  cement  should  be  mixed  dry,  water  gradually 
added  and  the  mixture  kept  constantly  agitated  by  pulling  it  up 
toward  the  high  side  of  the  box  with  a  hoe  until  it  attains  a  uniform 
consistency  like  thin  cream.  It  is  then  taken  out  by  scoop  shovels, 
placed  over  the  brick  to  be  filled,  which  have  just  previously  been 
thoroughly  sprinkled  with  water,  and  rapidly  broomed  back  arid  forth 
with  fiber  push  brooms  until  all  joints  are  full.  Because  of  the 
weight  of  the  coarse  particles  of  sand  and  fine  particles  of  cement, 
there  is  a  constant  tendency  for  the  sand  to  settle  out  of  the  liquid 
mixture  followed  by  the  cement,  thus  separating  the  ingredients.  To 
avoid  this  the  mixture  must  be  constantly  stirred,  while  being  placed 
on  the  pavement  in  small  amounts  at  a  time,  and  must  be  broomed 
quickly  into  the  joints.  Dumping  large  quantities  of  grout  onto  the 
pavement  and  allowing  it  to  flow  over  the  surface  and  into  the  joints 
is  a  sure  way  to  obtain  a  poor,  irregular  job  of  grouting.  The  ad- 
dition of  from  5  to  10  per  cent  by  weight  of  the  cement  of  hydrated 
lime  in  the  grout  mixture  also  aids  very  materially  in  preventing  the 
separation  of  the  ingredients,  making  a  much  more  plastic  and  sticky 
grout. 

After  making  one  application  of  grout  over  a  section  of  the 
pavement,  and  before  the  first  part  of  the  section  has  been  grouted 
for  longer  than  thirty  minutes,  the  grout  box  is  moved  back  and  a 
second  application  is  made,  this  time  of  a  little  thicker  consistency, 
to  completely  fill  all  the  joints  up  to  the  top  edges  of  the  brick.  It 
is  mixed  and  applied  in  the  same  way  as  before,  but  is  worked  back 
and  forth  over  the  joints  with  rubber  lipped  squeegees  until  the  joints 
are  full  and  no  surplus  remains  on  the  surface  of  the  brick.  If 
there  is  any  further  settlement  of  the  grout  in  the  joints  another  ap- 
plication like  the  second  should  be  made.  A  rubber  squeegee  can 
be  made  by  clamping  a  straight  piece  of  heavy  rubber  between  two 
boards  about  4  to  6  inches  wide  and  15  to  18  inches  long,  allowing 
the  rubber  to  project  a  couple  of  inches  beyond  the  edge  of  the 
boards  and  fastening  a  long  handle  to  the  boards.  The  grouting  at 
the  end  of  each  day  should  be  fully  completed  to  steel  plates  inserted 
between  two  rows  of  brick  in  order  to  obtain  a  vertical  joint.  These 
plates  are  withdrawn  as  soon  as  the  grout  has  stiffened.  After  the 
grout  has  hardened  sufficiently,  the  surface  of  the  pavement  should 
be  covered  with  an  inch  or  so  of  sand  or  dirt  and  the  covering  kept 
wet  during  the  time  the  cement  grout  is  curing.  The  curing  period 
should  never  be  less  than  one  week  and  should  preferably  last  two 
weeks  or  even  longer  in  cool,  wet  weather. 

No  traffic  of  any  kind  should  be  permitted  on  the  pavement 
during  the  curing  period.  The  protective  cohering  is  then  removed  and 
the  pavement  is  complete.  It  is  seen  that  the  placing  of  a  satis- 
factory cement  grout  filler  is  a  task  requiring  extreme  care  to  in- 
sure that  each  joint  is  filled  for  its  full  depth  with  a  dense,  homo- 
geneous cement  mortar  which  is  allowed  to  develop  its  full  strength 
under  favorable  conditions  for  hardening.  A  poor  cement  grout  is 
soon  little  better  than  a  sand  filler,  while  a  good  one  has  many 
advantages  to  recommend  it. 


LAYING  THE  BRICK  71 

Since  the  cement  filler  binds  the  individual  brick  into  one  solid, 
rigid,  continuous  slab,  some  means  should  be  provided  for  taking 
care  of  the  expansion  and  contraction  due  to  changes  in  tempera- 
ture. When  the  brick  slab  can  be  confined  rigidly  on  all  sides,  the 
expansion  can  be  taken  care  of  by  compression  stresses  in  the  brick. 
If  the  coefficient  of  expansion  of  brick  is  taken  at  0.0000040  per  de- 
gree F.,  a  raise  of  100  degrees  F.  in  a  confined  vitrified  brick  having 
a  modulus  of  elasticity  of  10,000,000  would  develop  a  confined  stress 
in  the  'brick  of  4,000  pounds  per  square  inch  or  about  one  fifth  of 
the  actual  crushing  strength  of  the  brick.  In  a  softer  brick  having 
a  modulus  of  elasticity  of  '5,000,000  the  confined  stress  would  be  2,000 
Ibs.  per  square  inch  or  again  about  one  fifth  of  the  crushing  strength 
of  this  quality  of  brick.  Accordingly  in  the  best  modern  practice  no 
allowance  is  made  for  longitudinal  expansion  in  a  cement  grouted 
brick  pavement,  the  expansion  being  taken  up  by  compressive  strains 
in  the  brick  and  grout.  Only  a  portion  of  the  theoretical  strains 
will  probably  be  realized  but  the  actual  strains  are  undoubtedly  pro- 
portional to  the  moduli  of  elasticity  which  in  turn  increase  with  the 
hardness  and  density  of  the  brick.  In  order  to  reduce  the  magni- 
tude of  these  stresses  where  cement  grout  filler  is  used,  therefore,  the 
brick  should  be  restricted  to  a  grade  sufficient  to  take  care  of  the 
abrasion  due  to  traffic  on  the  street  to  be  paved,  and  harder  brick 
should  be  excluded.  An  inspection  of  old,  cement  grouted,  brick 
streets  shows  the  softer,  less  dense  brick  have,  as  a  rule,  main- 
tained the  filler  intact,  providing  at  the  same  time  a  surface  capable 
of  resisting  moderate  traffic  conditions,  while  the  harder  and  denser 
brick  frequently  show  a  shattered  filler  and  no  wear.  The  existence 
of  these  compressive  strains  also  shows  the  absolute  necessity  for 
extreme  care  in  placing  and  curing  cement  grout  filler.  The  grout 
must  extend  the  full  depth  of  the  joint  or  the  brick  will  close  to- 
gether at  the  bottom  causing  them  to  'be  lifted  from  their  bed,  thus  dis- 
rupting the  pavement. 

Expansion  joints  placed  at  regular  intervals  across  the  street 
have  been  tried  to  relieve  pavement  expansion  strains  but  have  not 
proved  successful.  The  slab  between  expansion  joints  expands  but 
in  pulling  together  during  contraction  the  grout  breaks  away  from  the 
brick  on  account  of  the  tensile  strains  set  up.  The  cement  grout  is 
strong  in  compression  but  weak  in  tension.  Several  courses  of  brick 
each  side  of  the  expansion  joint  are  also  loosened  by  traffic  and  the 
grout  filler  soon  becomes  separated  from  the  brick,  and  broken  up. 

The  conditions  of  transverse  expansion  are  somewhat  different. 
Due  to  the  crown  of  the  pavement  the  slab  is  a  long,  slender,  curved 
column  and  compression  stresses  of  any  magnitude  would  cause  the 
slab  to  bend  still  more,  raising  it  off  the  bedding  course  and  possibly 
causing  longitudinal  tensile  cracks  to  form.  This  accounts  in  many 
cases  for  the  rumbling  sound  of  high  crowned,  grouted  brick  pave- 
ments. Either  the  sand  layer  has  settled  or  the  slab  has  been  raised 
off  of  its  bed  and  acts  as  a  sounding  board  for  passing  vehicles.  Curb- 
ing is  not  capable  of  sustaining  much  pressure.  For  these  reasons 
a  longitudinal  expansion  joint  should  be  provided  along  each  side  of 
the  grouted  brick  pavement.  Since  the  computed  amount  of  expan- 
sion in  a  brick  slab  50  feet  wide  for  a  100  degrees  F.  rise  in  tem- 
perature is  0.24  inch,  half  of  which  may  be  assumed  to  be  taken  at 
each  curb,  expansion  joints  of  one  half  to  one  inch  in  width  along 
each  curb  should  be  ample.  Provision  is  made  for  the  longitudinal 


72  LAYING  THE  BRICK 

expansion  joints  when  the  brick  are  being  laid  by  placing  a  slightly 
beveled  board  of  the  proper  thickness  and  depth  next  the  curb  and 
laying  the  brick  against  it.  After  the  brick  have  been  rolled  and 
grouted  and  the  grout  has  set  sufficiently,  this  board  is  removed  and 
the  space  cleaned  out  and  filled  with  hot  asphaltic  cement,  or  some 
of  the  numerous  prepared  expansion  joint  fillers  may  be  used.  These 
prepared  joints  come  in  convenient  lengths  of  a  specified  width  and 
thickness  and  can  be  laid  on  edge  against  the  curb  before  laying  the 
brick.  In  any  case,  the  completed  joint  to  be  of  value  must  be  equally 
compressible  throughout  its  length  and  depth,  and  pebbles,  dirt,  sand 
or  grout  should  not  be  allowed  to  get  into  the  joint  before  pouring 
the  asphalt. 

At  about  the  time  cement  grout  came  into  use  as  a  brick  filler, 
pitch  was  used  to  a  considerable  extent.  The  old  pitch  filled  streets 
were  not  always  successful,  chiefly  because  no  tests  were  imposed  to 
determine  the  suitability  of  the  filler  and  contractors  used  whatever 
they  could  get  the  cheapest,  from  a  pitch  that  was  so  soft  in  summer 
it  would  run  out  of  the  joints  and  into  the  gutters,  to  one  which  was 
so  hard  and  brittle  in  cold  weather  that  it  would  powder  up  and  chip 
out  of  the  joints  under  traffic.  At  present  it  is  possible  to  pur- 
chase a  pitch  under  the  most  rigid  requirements  made  especially  for 
brick  filler.  The  tar  manufacturers  are  also  recommending  that 
engineers  use  a  softer  grade  of  pitch,  mix  it  when  hot  with  equal  parts 
of  hot  sand,  and  run  this  mixture  into  the  joints.  It  is  claimed  that 
such  a  mixture  will  make  a  tough,  pliable,  resilient  filler  at  all  or- 
dinary street  temperatures.  Asphaltic  cement  has  more  recently 
come  into  use  as  a  bituminous  filler.  This  is  due  to  the  reduced 
price  of  asphalt  and  to  the  fact  that  it  can  be  purchased  in  any 
quantity  under  nearly  any  test  requirements  that  guarantee  its  per- 
manence, pliability,  toughness  and  resiliency  under  all  weather  con- 
ditions. Tar  is  more  adhesive  and  more  liquid  when  heated  but 
asphaltic  cement  is  much  less  susceptible  to  changes  of  temperature 
than  tar  and  on  account  of  its  toughness  and  cohesion  makes  a  very 
satisfactory  brick  filler. 

The  asphaltic  cement  is  heated  in  proper  kettles  from  350  to 
400  degrees  F.  so  that  it  will  flow  easily  and  is  flushed  over  the  sur- 
face of  the  brick  after  they  have  been  laid  and  rolled.  It  is  worked 
back  and  forth  with  hot  iron  squeegees  until  the  joints  are  completely 
filled.  The  heating  kettle  should  be  equipped  with  a  thermometer 
so  that  all  the  asphalt  may  be  poured  at  the  same  temperature  and 
will  not  be  burned  by  overheating.  The  brick  surface  must  be  clean 
and  dry  and  the  asphalt  should  preferably  be  poured  in  warm  weather. 
Better  adhesion  between  the  asphalt  and  brick  is  obtained  if  the  filling 
of  the  joints  follow  close  behind  the  rolling,  so  that  the  surface  of 
the  brick  does  not  become  coated  with  dust  or  dirt.  The  hot  asphalt 
from  the  pouring  can  should  cover  all  parts  of  the  brick  surface 
and  none  of  the  chilled  asphalt  on  the  surface  of  the  pavement  should 
be  squeegeed  over  unfilled  joints,  as  it  is  liable  to  bridge  the  joints 
without  filling  them.  The  squeegees  are  plates  of  iron  y±  to  V2  inch 
thick,  2  to  4  inches  wide  and  15  to  18  inches  long  with  the  lower 
edge  beveled;  the  plate  being  welded  to  a  long,  iron  shanked,  asphalt- 
rake  handle.  Several  of  these  should  be  provided  so  that  one  set  may 
be  heating  in  the  fire  pot  of  the  asphalt  kettle  while  the  others  are 
in  use.  The  hot  iron  keeps  the  asphalt  liquid  and  allows  it  to  be 


74  LAYING  THE  BRICK 

worked  over  the  joints  until  they  are  full  leaving  but  a  thin  coating 
on  the  surface  of  the  brick.  Hot,  coarse  sand  should  then  be  scat- 
tered over  the  surface  in  sufficient  quantities  to  take  up  the  surplus 
asphalt.  This  sand  layer  is  much  improved  by  rolling,  additional 
sand  being  added  wherever  the  asphalt  comes  to  the  surface.  This 
form  of  construction  builds  up  a  sand-asphalt  carpet  from  an  eighth 
to  a  quarter  inch  thick  on  the  surface  of  the  pavement  which  allows 
the  joints  to  become  packed  full  by  traffic  where  settlement  occurs 
and  evens  up  slight  inequalities  in  the  surface.  Under  much  traffic 
it  disappears  during  the  first  few  years,  as  it  is  not  intended  to  be 
wear  resisting  but  is  simply  an  incident  to  an  easy,  economical  method 
of  filling  the  joints.  The  exposed  reticular  wire-cut  surface  of  the 
Vertical  Fiber  type  of  brick  forms  an  excellent  bond  with  the  asphalt, 
which  adheres  much  better  and  lasts  longer  on  the  surface  of  this  kind 
of  brick.  If  desired,  this  carpet  can  be  maintained  on  residence 
streets  by  subsequent  applications  of  heavy  asphaltic  road  oil,  when- 
ever necesary,  but  this  is  seldom  justifiable  on  account  of  the  main- 
tenance cost.  The  asphaltic  cement  used  for  joint  filler  should  be  of 
the  best  quality  obtainable,  and  should  be  tested  for  permanence,  for 
ductility,  viscosity,  and  susceptibility  to  temperature.  In  character 
and  consistency,  it  should  be  the  equal  of  the  kind  used  in  the  best 
sheet  asphalt  pavements. 

Since  each  brick  is  surrounded  by  a  resilient  filler,  no  further 
provision  need  be  made  for  expansion  and  contraction.  Traffic  can 
also  be  allowed  over  the  pavement  as  soon  as  the  filling  of  the  joints 
is  compelted.  Engineers  are  more  or  less  divided  in  their  opinion  as 
to  whether  cement  grout  or  asphaltic  cement  filler  is  the  best  for 
brick  pavements,  and  there  have  been  many  wordy  controversies  by 
the  advocates  of  each.  No  doubt  there  have  been  failures  of  both 
kinds  of  fillers  as  well  as  many  good  examples  of  each.  There  are 
so  many  good  points  about  each  of  these  fillers  that  a  few  failures 
due  to  inexperience,  poor  material,  or  careless  workmanship  ought  not 
to  condemn  that  material  for  all  future  work.  Both  cement  grout  and 
asphaltic  cement  have  many  advantages  as  well  as  some  disadvantages, 
and  the  engineer  should  recognize  these  and  use  that  filler  which 
is  best'  adapted  for  the  conditions  of  traffic.  The  advantages  of  using 
a  cement  grout  filler  may  be  summed  up  as  follows: 

(1)  It  waterproofs  the  joints,  preventing  surface  water  from 
reaching  the  foundation;  (2)  it  adds  strength  to  the  pavement,  dis- 
tributing the  traffic  loads  over  a  large  area  of  foundation,  and  bridg- 
ing slight  settlements:  (3)  it  is  cheap  in  first  cost  and  the  main- 
tenance cost  is  very  low;  (4)  as  long  as  it  fills  the  joints  and  re- 
mains intact,  it  protects  the  edges  of  the  brick  from  being  broken  or 
chipped,  thus  increasing  the  service  and  life  of  the  brick;  and  (5) 
it  makes  a  clean,  sanitary  surface  and  one  easily  kept  clean.  The 
disadvantages  of  cement  grout  as  a  filler  for  brick  may  be  itemized  as : 
(1)  on  busy  city  streets  it  is  difficult,  often  impossible  to  keep  traffic 
off  of  the  completed  pavement  long  enough  for  the  grout  to  become 
hard;  02)  it  is  difficult  to  make  openings  in  the  pavement,  and  more 
difficult  to  repair  them  properly  and  protect  them  from  traffic  for 
the  ten  days  necessary  for  the  hardening  of  the  grout;  (3)  cement 
grout  makes  a  slick  pavement  and  cannot  be  used  on  heavy  grades 
for  traffic  except  with  a  grooved  or  "hillside"  brick;  (4)  a  cement 
grouted  brick  pavement  laid  on  a  plain  sand  bed  is  more  noisy  than 


76  LAYING  THE  BRICK 

where  a  bituminous  filler  is  used;  (5)  the  cement  grout  binds  the  in- 
dividual brick  into  a  solid,  rigid  slab  subject  to  the  strains  of  expan- 
sion and  contraction  which  may  shatter  brick  of  weak  internal  struc- 
ture or  cause  unsightly  cracks  to  appear;  (6)  the  cement  grout  is  very 
difficult  to  properly  mix,  place  and  cure  and  requires  skillful  handling 
and  rigid  supervision;  and  (7)  once  placed  it  is  difficult  to  correct 
or  repair  defective  grout  filler. 

On  the  other  hand  the  advantages  of  an  asphaltic  cement  filler 
may  be  enumerated  as  follows:  (1)  traffic  may  be  turned  on  the  pave- 
ment as  soon  as  the  filler  is  in  place  thus  closing  the  street  a 
minimum  length  of  time;  (2)  plumber's  cuts  and  other  openings  in 
the  street  can  be  more  easily  made  and  repaired  than  with  a  cement 
grout  filler;  (3)  it  is  easier  on  horses  feet  and  the  soft  joint  gives  a 
good  foothold  on  all  grades;  (4)  it  can  be  easily  and  successfully 
manipulated  on  the  street  and  there  is  no  expense  of  protecting  and 
curing  it  after  it  is  in  place  with  the  attendant  possibility  of  damage 
by  rain,  frost  or  premature  traffic;  (5)  it  makes  practically  a  nois- 
less  pavement;  (6)  all  troubles  from  expansion  and  contraction  are 
done  away  with;  (7)  it  forms  an  elastic  cushion  all  around  each  brick, 
protecting  them  from  the  shock  of  blows  and  allows  slight  adjust- 
ments in  the  position  of  the  brick  to  care  for  shrinking  or  settling 
of  the  sand  bed,  and  (8)  it  provides  a  flexible  waterproof  joint,  which 
is  easily  maintained.  The  disadvantages  of  asphalt  filler  may  be  sum- 
marized as:  (1)  it  is  more  expensive  in  first  cost  and  requires  more 
maintenance  than  a  good  cement  grout  filler;  (2)  under  horse  and 
steel  tired  traffic  it  does  not  wear  as  well  or  protect  the  edges  of  the 
brick  from  chipping;  (3)  it  does  not  distribute  the  loads  over  as 
great  an  area  of  base  and  consequently  does  not  make  as  strong  a 
pavement  as  cement  grout  filler;  (4)  it  is  not  as  easily  cleaned  and 
makes  a  more  or  less  dirty  surface  the  first  year  after  being  placed; 
and  (5)  the  asphalt  will  pack  down  and  settle  into  the  joints. 

No  one  kind  of  filler  should  be  used  to  the  exclusion  of  all 
others  in  general  paving  work.  It  is  seen  that  the  advantages  of 
Portland  cement  grout  filler  recommend  it  for  use  on  country  high- 
ways, alleys,  and  on  all  streets  where  there  is  a  large  percentage  of 
horse-drawn  traffic  where  most  of  the  disadvantages  named  do  not 
have  much  weight.  On  steep  grades,  on  residence  or  retail  business 
streets,  and  on  streets  which  are  being  constantly  torn  up  or  where 
the  traffic  is  mainly  automobiles,  asphalt  makes  the  most  satisfac- 
tory joint  filler. 

With  the  idea  of  making  asphalt  filled  brick  pavement  more 
serviceable  and  durable  under  severe  traffic  conditions,  some  cities 
have  recently  specified  a  wire-cut  paving  block  without  lugs.  The 
first  brick  used  in  pavements  had  no  lugs,  and  it  was  not  until  cement 
grout  filler  came  into  use  that  any  necessity  arose  for  wider  joints 
between  the  brick.  Lugs  on  paving  brick  were  introduced  to  make  a 
wide,  uniform  joint  between  the  rows  of  brick  and  so  give  sufficient 
body  to  the  grout  to  insure  its  strength  and  allow  it  to  fill  the  joint 
completely  to  the  bottom.  The  joints  in  any  iform  of  block  pavement 
are  usually  the  places  where  the  first  signs  of  wear  occur,  and  in 
all  other  block  pavements,  every  effort  is  made  to  make  the  joints  as 
narrow  as  possible.  The  closer  the  blocks  are  set,  the  more  support 
they  lend  one  another,  the  less  opportunity  there  is  for  broken  cor- 
ners, and  the  smoother  will  be  the  wearing  surface.  Where  asphalt 
is  used  as  a  filler  for  brick  pavement,  narrow  joints  are  especially 


LAYING  THE  BRICK  77 

desirable  as  the  brick  material  will  then  receive  all  the  wear  leaving 
the  filler  to  perform  the  functions  of  waterproofing  the  surface 
and  providing  a  thin  elastic  cushion  for  each  block.  Brick  cannot  be 
made  true  enough  to  shape  nor  need  they  be  laid  so  close  together 
that  there  is  not  some  space  between  them  which  will  be  penetrated 
by  the  hot  asphalt.  It  is  probable  that  even  where  cement  grout 
filler  is  used,  narrow  jointed  brick  pavement  will  prove  the  most 
satisfactory.  The  brick  material  is  so  much  stronger  and  more  cap- 
able of  resisting  the  abrasive  wear  of  traffic  than  the  grout,  that  a 
brick  wearing  surface  which  does  not  depend  on  the  joint  filler  will 
undoubtedly  be  more  durable.  The  effect  of  the  impact  of  heavy  loads 
in  crossing  from  one  block  to  another  is  also  considerably  lessened, 
and  experience  has  proven  that  on  account  of  this  fact,  a  narrow 
jointed  block  pavement  will  wear  smoother  and  give  better  service 
than  one  with  wide  joints.  On  heavy  traffic  streets  where  the  lugless 
type  of  brick  pavement  has  been  used,  the  results  have  more  than 
justified  all  of  these  contentions. 

The  ordinary  cement  grouted  brick  pavement  presents  the 
anomaly  of  two  superimposed  beams,  the  foundation  and  the  brick 
slab,  separated  by  a  sand  or  a  sand-cement  layer  having  no  strength 
as  a  beam.  The  two  beams  acting  separately  are  not  only  much  weaker 
than  if  they  were  joined  together  but  the  interposing  of  an  inert  ma- 
terial also  lowers  their  resistance  to  thermal  changes  and  to  impact. 
It  has  been  shown  that  the  chief  function  of  the  cushion  layer  is  to 
provide  a  uniform  bed  or  bearing  for  each  individual  brick.  If, 
therefore,  a  satisfactory  bed  can  be  provided  for  each  brick,  and  if 
the  entire  brick  surface  can  at  the  same  time  be  bonded  to  the  base 
so  that  the  foundation  and  wearing  surface  will  act  as  one  beam, 
economy  of  construction  and  a  stronger  pavement  will  result.  The 
monolithic  type  of  brick  pavement  accomplishes  this  by  bedding  the 
brick  in  the  soft  concrete  base,  rolling  them  lightly  to  an  even  surface 
and  immediately  filling  the  joints  with  Portland  Cement  grout  so  that 
the  foundation,  the  brick,  and  the  grout  filler  set  into  one  solid,  well 
bonded  mass.  This  form  of  construction  had  been  tried  only  on  small 
areas  until  about  two  years  ago,  but  a  piece  at  Terre  Haute,  Ind.,  now 
twelve  years  old  is  reported  to  be  in  good  condition  with  no  surface 
defects  and  showing  only  such  wear  as  might  be  normally  attributed 
to  heavily  concentrated  traffic.  A  satisfactory  method  of  constructing 
monolithic  brick  pavement  has  been  devised  and  in  the  past  two 
years  a  considerable  amount  of  it  has  been  laid  on  country  highways 
and  some  on  city  streets.  In  building  country  roads  twenty  feet  or 
less  in  width,  the  sub-grade  is  first  roughed  out  and  steel  sideforms 
firmly  set  at  the  sides  of  the  pavement  with  their  top  true  to  line 
and  grade.  The  sub-grade  is  trimmed,  templeted  and  rolled  and  a 
well-mixed,  quaking  concrete  is  deposited  and  leveled  by  shovels  about 
an  inch  or  two  above  the  top  level  of  the  foundation.  This  concrete 
is  then  drawn  down  to  a  true  even  surface  by  an  ingeneously  devised 
templet.  The  templet  consists  of  a  steel  I-beam  for  the  forward  cut- 
ting edge  and  a  steel  channel  with  flanges  placed  outward  for  a  rear 
cutting  edge,  making  in  fact  a  double  templet.  The  I-beam  and  chan- 
nel are  bent  to  the  proper  crown  of  the  pavement,  are  rigidly  braced 
and  connected  together  with  a  space  of  two  or  three  feet  between 
them  and  are  supported  on  the  side  forms  by  a  frame  and  rollers 
which  prevent  tipping  as  it  is  drawn  forward.  The  cutting  edge  of 


LAYING  THE  BRICK 


79 


the  I-beam  in  front  is  about  a  quarter  of  an  inch  below  the  lower 
edge  of  the  rear  channel.  In  operation  the  space  between  the  two 
templets  is  filled  with  dry  cement  and  sand  mixed  in  the  proportions 
used  for  the  mortar  in  the  concrete.  A  forward  movement  of  the 
templet  first  cuts  off  the  concrete  and  then  fills  all  irregularities  in 
the  surface  with  the  mortar  mixture.  The  surface  thus  created  is  re- 
markably smooth  and  is  similar  in  appearance  to  the  ordinary  cement- 


Fig-.  34 — Before  Grouting  Monolithic  Brick  Pavement  (Several  Brick  re- 
moved to  show  through  bedding  on  the  green  concrete  foundation.) 

sand  cushion  course.  In  another  method,  the  concrete  is  drawn  by 
means  of  a  single  steel  or  steel  shod  templet,  sprinkled  lightly  with 
a  dry-mixed  cement  and  sand  and  immediately  tamped  with  a  "slap- 
stick" or  box  shaped  templet  about  twelve  inches  wide  until  mortar 
flushes  to  the  surface  and  the  concrete  is  shaped  to  a  true  cross  sec- 
tion. The  brick  are  laid  immediately  on  the  surface  of  the  concrete 


80  LAYING  THE  BRICK 

as  prepared.  If  the  concrete  has  been  mixed  to  a  quaking  consistency 
but  not  sloppy,  no  difficulty  is  experienced  in  laying  the  brick  in  the 
usual  maner,  the  bricklayer  standing  on  the  brick  already  in  place 
and  having  them  brought  to  him  on  pallets  or  in  clamps.  Boards  laid 
on  the  surface  for  the  carriers  to  walk  on  is  an  additional  precau- 
tion against  displacing  any  of  the  brick  after  laying.  With  ordinary 
care  there  is  little  trouble  in  getting  a  true,  even  surface  to  the  brick. 
The  brick  are  then  rolled  with  a  sectional  hand  roller  weighing  from 
four  tp  five  hundred  pounds  until  all  the  brick  are  evenly  bedded  and 
the  surface  is  smooth.  As  soon  as  possible  after  the  brick  are  culled 
but  within  an  hour  or  so  after  they  have  been  laid,  the  joints  are 
filled  with  Portland  Cement  grout  with  the  same  care  and  in  the 
same  manner  as  described  in  this  chapter.  Concrete  work  is  stopped 
early  enough  in  the  day  so  that  all  concrete  placed  each  day  may  be 
covered  with  brick  and  the  whole  grouted.  The  concrete  should  be 
spaded  and  finished  against  a  vertical  plank  set  across  the  road  at  the 
end  of  the  day's  work  and  the  brick  laid  up  to  this.  Where  the  double 
steel  templet  is  used  the  grout  is  kept  back  five  or  six  courses  from 
this  plank  by  inserting  steel  plates  between  two  rows  of  brick.  On 
beginning  work  the  next  day,  these  last  ungrouted  courses  of  brick 
are  removed,  allowing  room  for  the  rear  templet  so  that  the  forward 
templet  may  cut  down  the  first  of  the  concrete  placed. 

In  paving  streets  or  roads  wider  than  20  feet,  it  is  difficult  to 
drag  the  concrete  and  the  luting  mixture  in  one  operation  and  a 
slightly  different  method  must  be  used.  The  concrete  is  placed  and 
tamped  with  a  heavy  templet  about  a  quarter  or  half  an  inch  below 
the  bottom  of  the  brick  course  as  described  in  the  chapter  on  founda- 
tion. Before  this  concrete  has  attained  its  final  set,  a  cement  mortar 
mixed  with  enough  water  to  make  it  work  easily  is  spread  over  the 
concrete  and  dragged  to  a  true  uniform  surface  with  a  steel  templet 
or  a  wood  templet  with  a  steel  plate  edge.  This  mortar  coat  is  luted 
by  hand  over  intersections  or  at  warps,  in  the  pavement  where  it  is 
not  possible  to  use  the  templet  and  me  brick  are  laid,  rolled  and 
grouted  as  on  the  narrow  pavements.  The  pavement  must  be  covered, 
protected  and  cured  so  that  the  grout  will  attain  its  full  strength 
before  traffic  is  allowed  over  it,  but  since  the  foundation  concrete  and 
grout  are  curing  simultaneously,  the  time  which  is  ordinarily  allowed 
for  the  concrete  to  set  before  laying  the  brick  is  saved. 

The  design  and  use  of  a  proper  templet  has  made  possible  the 
economical  construction  of  a  monolithic  brick  pavement  with  the  re- 
sult that  a  solid,  rigid  masonry  pavement  slab  is  obtained  with  each 
brick  bonded  to  its  neighbors  and  to  the  foundation.  That  such  a 
slab  acts  as  a  monolith  is  proved  by  recent  tests  made  by  the  Civil 
Engineering  Department  of  the  University  of  Illinois.  Three  slabs 
were  built  of  wire  cut  brick,  six  coures  wide  and  five  brick  in  each 
course,  making  the  outside  dimensions  23  by  45  inches.  The  first 
slab  consisted  of  4  inches  of  1-2-4  concrete  covered  with  one  eighth 
inch  of  1  to  5  dry  mixed  sand  and  cement,  with  a  three  inch  brick 
tamped  into  the  green  concrete  and  grouted  with  a  1  to  1  mixture. 
Slab  two  was  the  same  as  one  except  that  four  inch  depth  brick 
was  used.  Slab  three  consisted  of  4  inch  depth  brick  laid  on  a  one  inch 
base  of  dry-mixed,  one  to  three  cement  mortar  and  grouted  with  a 
1  to  1  mixture.  As  a  check  on  these  slabs  a  fourth  slab  of  the  same 


LAYING  THE  BRICK  81 

size  was  made  of  1-2-3  concrete  7  inches  thick  using  a  good  gravel 
aggregate.  All  the  slabs  were  allowed  to  set  24  hours,  then  covered 
with  sand  and  kept  moist  for  27  days,  and  tested  as  simple  beams  of 
42  inch  span  with  the  load  applied  at  the  third  points. 

TESTS  OF  MONOLITHIC  BRICK  SLABS. 

Total  Thickness  Thickness          Total       Modus  of  Rup- 

SlabNo.      Thickness  Base  Brick  Load  ture  Lbs. 

Los  Per  Sq.  Inch 

1  7-3/16  in.  4-3/16  in.  3  in.  13,100  465 

2  8-1/4  in.  4-1/4     in.  4  in.  21,500  580 

3  5  in.  1  in.  4  in.  6,700  490 

4  7-1/16  in.  7-1/1S  in.  12,500  460 

The  results  showed  that  the  brick  slabs  acted  as  monoliths  and 
with  higher  moduli  of  rupture  than  plain  concrete.  The  bond  be- 
tween the  brick  was  perfect  but  some  weakness  was  shown  by  the 
eighth  inch  bedding  course  of  1  to  5  mortar.  It  was  recommended 
that  this  bedding  course  be  made  richer  and  of  the  same  proportions 
as  the  mortar  for  the  concrete  base. 

The  chief  advantages  of  the  monolithic  type  of  brick  pavement 
construction  may  be  stated  as  (1)  it  eliminates  the  hazard  of  the 
sand  cushion  both  during  construction  and  during  use,  (2)  it  does 
away  with  the  necessity  of  a  curbing  or  edging  on  country  roads,  (3) 
the  grout  filler  remains  intact  since  there  is  no  chance  for  slight  set- 
tlements or  movement  of  the  brick  causing  the  bond  between  the 
brick  to  be  broken,  (4)  each  brick  is  assured  a  cement  bond  for  its 
entire  depth  even  if  the  mortar  works  up  in  the  joints  slightly  dur- 
ing rolling,  (5)  since  the  foundation  and  brick  surface  act  as  one 
unit,  thermal  effects  are  cared  for  without  inducing  unusual  strains 
in  the  paving  material,  (6)  there  being  no  chance  for  shrinkage  of 
the  bed,  all  rumbling  of  the  pavement  is  eliminated,  and  (7)  the  ordi- 
nary concrete  foundation  c^n  be  reduced  in  depth  as  the  brick 
slab  may  be  depended  upon  t^take  its  share  of  the  load. 

The  majority  of  engineers  are  of  the  opinion  that  the  mono- 
lithic brick  pavement  offers  wonderful  possibilities  in  permanent 
highway  construction  at  consi^rable  saving  in  cost  over  former 
methods  of  construction.  It  seems  probable  that  a  four  inch  con- 
crete foundation  with  a  two  and  one  half  inch  or  three  inch  depth 
brick  of  this  type  laid  on  a  we'll  prepared  subgrade  will  be  amply 
strong  to  withstand  the  heaviest  highway  traffic.  In  resurfacing 
old  macadam  roads  where  the  macadam  base  is  satisfactory,  the  top 
of  the  old  macadam  can  be  cleaned  off,  repairs  made  to  the  base,  de- 
pressions leveled  up  and  the  surface  rolled  and  watered  to  a  firm,  tight 
condition.  An  inch  or  two  of  rich  cement  mortar  or  fine  concrete 
can  then  be  templeted  over  this  old  surface  and  three  or  four  inch 
depth  brick  laid.  Such  a  form  of.  construction  would  be  economical 
and  satisfactory,  however,  only  when  the  old  macadam  was  very 


close  to  the  proper  grade,  was  ( 
base  was  amply  thick  and  in  goo( 
Even  when  care  is  taken 
types  of  brick  pavements,  traffic 
in  any  pavement  and  slight  su 
should  be  taken  care  of  as  soor 


f  the  proper  width,  and  where  the 

condition, 
in  the   construction   of  the  various 

soon  searches  out  the  weak  spots 
face    defects    may   appear.       These 

as  they  appear,  especially  all  de- 


pressions and  rough  spots  should  ;be  corrected.     Impact  is  much  more 


82 


LAYING  THE  BRICK 


damaging  to  a  pavement  than  abrasive  wear,  and  if  the  surface  is 
kept  up  to  grade  and  smooth,  the  life  of  a  pavement  is  very  much  in- 
creased. If  a  brick  pavement  is  gone  over  thoroughly  in  this  way 
after  the  first  or  second  year  it  has  been  down,  the  cost  will  be  slight 


35 — No  Curb  Edging  Required  for  Monolithic  Brick  Paved   Highways 


LAYING  THE  BRICK 


83 


depending  on  the  care  in  construction,  and  little  further  repairing  will 
be  necessary.  Where  bituminous  joint  filler  has  been  used,  the  joints 
should  be  maintained  full,  additional  material  being  added  every  three 
or  four  years  if  conditions  of  traffic  demand  it.  On  country  roads, 
ditches  should  be  cleaned  out,  culverts  and  drains  kept  open  and  the 
shoulders  trimmed  and  leveled.  Broken  and  soft  brick  should  be 
removed,  cracks  filled  with  hot  tar  or  asphalt,  worn  brick  turned  and 
other  needful  attention  given  to  the  pavement  from  time  to  time  in 


Po&'hon  ofho/es  for3//jch 
&o//er  for  different 'c/ep/h<s  of 
wearing  Surface. 


J&*$4 


Fig.   36. — Construction  of  Double  Templet  Recommended  for  Building 
Monolithic  Brick  Pavements. 


order  to  preserve  the  original  investment  in  the  highest  state  of  ef- 
ficiency. A  well  built  brick  pavement  will  go  longer  and  wear  bet- 
ter without  any  maintenance  than  any  other  kind  of  pavement,  except, 
possibly  granite  blocks.  It  is,  however,  that  much  better  for  hav- 
ing some  attention  from  time  to  time  and  the  cost  is  so  little  as  to 
more  than  repay  in  durability  alone.  For  example  Mr.  H.  F.  Breed, 
First  Deputy  Highway  Commissioner  of  the  New  York  State  High- 
way Department,  recently  reported  that  the  cost  of  maintaining  290 
miles  of  brick  paved  roads  of  all  ages  for  the  year  1915  was  $176.00 


84  LAYING  THE  BRICK 

per  mile  including  some  not  on  concrete  foundation.  Eliminating 
these  latter,  the  cost  averaged  only  $131.00  per  mile.  These  figures 
include  cleaning  ditches,  fixing  shoulders  maintaining  guard  rail, 
patrolling,  etc.,  and  he  states  that  the  amount  spent  on  the  pavement 
itself  was  not  more  than  30  to  40%  of  this  total.  In  some  cases  for  a 
series  of  years  there  is  practically  no  cost  to  the  brick  pavement 
proper.  In  comparison  he  states  that  the  average  cost  of  maintain- 
ing, for  1915,  gravel  roads  was  $577.00  per  mile,  waterbound  maca- 
dam $564.00,  bituminous  macadam  penetration  method  $448.00,  bi- 
tuminous macadam  mixing  method  $181.00,  concrete  pavement  requir- 
ing surface  treatment  $532.00,  and  concrete  pavement  $129.00.  Old 
brick  pavements  in  which  the  joints  have  been  allowed  to  deteriorate 
may  often  be  effectively  treated  by  thoroughly  cleaning  all  loose 
material  from  the  joints  and  the  surface  of  the  pavement,  and  when 
the  surface  is  warm  and  dry  flushing  it  over  with  an  adhesive,  high 
grade  asphalt  or  tar,  absorbing  the  surplus  with  a  liberal  coating  of 
hot  sand  or  stone  chips. 

A  serious  problem  which  is  acute  in  large  cities  is  the  con- 
stant opening  of  pavements  for  underground  pipe  or  conduit  con- 
nections or  extensions.  Many  attempts  have  been  made  to  solve  this 
so  that  no  damage  will  be  done  to  the  pavement,  but  none  of  them 
have  proved  entirely  satisfactory  or  workable.  The  municipal 
authorities  should  have  complete  control  of  all  openings  made  in  the 
streets  and  should  see  that  the  backfilling  of  the  trench  is  properly 
done.  The  actual  repairing  of  the  pavement  should  be  done  by  city 
forces.  The  old  pavement  and  foundation  should  be  cut  back  on  an 
upward  bevel  so  that  the  patch  of  concrete  foundation  will  have  a 
bearing  of  at  least  six  inches  or  undisturbed  ground  each  side  of  the 
trench  and  fit  the  old  foundation  like  the  keystone  of  an 
arch.  The  brick  surfacing  should  be  toothed  back  each  way  and  no 
bats  or  broken  brick  should  be  left  in.  The  bedding  course  must  be 
carefully  trued  and  the  new  brick  firmly  and  evenly  bedded,  great 
care  being  taken  that  the  edges  of  the  patch  exactly  conform  to  the 
old  pavement.  The  filler  may  then  be  placed  and  the  patch  barri- 
caded until  the  concrete  has  attained  sufficient  strength  for  traffic. 
To  properly  backfill  and  repair  an  opening  in  a  pavement  is  a  pains- 
taking and  costly  task,  and  the  corporation  or  property  owner  caus- 
ing the  cut  to  be  made  should  be  compelled  to  pay  the  full  cost. 

Some  cities  charge  the  cost  of  repairs  and  a  fixed  sum  of  $10 
to  $50  as  a  penalty  for  opening  the  pavement  within  the  first  year 
after  it  is  down.  Others  serve  thirty  days  notice  on  all  property 
owners  of  the  city's  intention  to  pave  and  then  refuse  all  permits, 
except  in  a  case  of  emergency  for  the  first  year  or  two  after  the  pave- 
ment is  completed.  There  seems  to  be  no  way,  however,  of  absolute- 
ly preventing  the  opening  and  damaging  of  pavements  in  cities  and  the 
best  method  of  reducing  the  number  and  the  making  of  proper  repairs 
must  be  left  to  the  individual  municipality. 

From  this  discussion  it  is  seen  that  methods  of  constructing 
brick  pavements  as  well  as  the  manufacture  of  material  from  which 
they  are  made,  is  being  constantly  improved  from  the  standpoint  of 
economy  as  well  as  better  service.  In  fact  engineers  are  of  the 
opinion  that  the  pavements  of  the  future  will  be  constructed  of  the 
few  standard  materials  of  present  day  use  with  a  continual  improve- 
ment in  construction  methods.  Each  pavement  should  be  constructed 


LAYING  THE  BRICK  85 

of  the  highest  type  of  that  kind.  Traffic  is  increasing  so  enormously 
even  on  country  roads  that  any  defective  material  or  workmanship,  or 
weak  or  inadequate  pavement  construction  is  soon  disclosed.  If  there 
is  one  thing  which  has  been  emphasized  in  this  discussion  it  is  that  the 
entire  design  and  construction  of  the  pavement  should  be  carried  out 
to  produce  uniform  strength  and  uniform  wearing  qualities.  No  one 
ever  saw  a  brick  pavement  really  worn  out;  they  have  failed  through 
lack  of  proper  maintenance  attention,  weak  foundation,  bad  joints, 
variable  quality  of  brick,  wrongful  use  by  traction  engines,  excessive 
loads  or  service  cuts. 

From  past  experience  and  present  knowledge,  it  appears  that 
there  are  three  standard  types  of  brick  pavement  construction  which 
may  be  used  with  the  assurance  of  obtaining  a  high  class  and  emi- 
nently satisfactory  surface,  namely:  first,  a  bituminous  filled  narrow 
jointed  brick  surface  bedded  on  cement  sand  and  supported  by  a  con- 
crete foundation,  second  the  same  type  of  construction  except  that 
the  joints  are  filled  with  a  rich  Portland  cement  grout  and  third  the 
monolithic  construction,  the  joints  being  filled,  of  course,  with  cement 
grout.  By  varying  the  depth  of  the  foundation  to  suit  the  subsoil  and 
traffic  conditions  and  by  selecting  a  depth  and  quality  of  paving  brick 
which  will  best  answer  the  conditions  of  traffic,  the  highway  engi- 
neer can  build  economical  and  durable  pavements.  In  drawing  his 
specifications  and  in  supervising  the  work,  he  must  remember,  how- 
ever, that  he  is  the  agent  of  the  contractor  as  well  as  of  the  property 
owner.  On  the  property  owner's  side,  he  should  insist  on  the  work 
and  material  complying  with  the  requirements  of  the  specifications 
and  see  that  the  specifications  contain  everything  needful  to  compel 
a  first  class  piece  of  work  but  nothing  which  adds  additional  cost 
without  a  commensurate  increase  in  the  utility  of  the  pavement. 
For  the  contractor's  sake,  the  specifications  should  be  complete  and 
clear,  containing  nothing  which  it  is  not  expected  to  enforce,  and  con- 
cisely setting  forth  all  the  requirements  which  must  be  complied  with. 
Indefinite  clauses  such  as  "to  the  satisfaction  of  the  engineer"  should 
be  avoided  in  any  specification  as  they  are  almost  certain  to  be  a 
source  of  trouble  and  a  definite  statement  of  exactly  what  will  satisfy 
the  engineer  or  will  be  directed  by  him  should  be  substituted.  A 
clear  understanding  of  the  standard  of  material  and  workmanship 
to  be  maintained  is  helpful  to  all  three  parties — the  property  owner, 
the  contractor,  and  the  engineer.  The  engineer  should  not  seek  to 
cover  up  his  own  mistakes  by  trying  to  compel  the  contractor  to  do 
more  than  is  required  by  his  contract.  On  the  other  hand,  in  spite 
of  good  intentions  on  the  part  of  the  contractor,  the  work  may  not 
prove  satisfactory  unless  each  operation  is  carefully  supervised.  The 
laborers  and  workmen  are  very  liable  to  become  careless  and,  through 
lack  of  proper  equipment,  organization  or  knowledge,  a  poor  piece  of 
work  may  result.  A  representative  of  the  engineer  who  understands 
pavement  construction  work  and  knows  the  requirements  of  the 
specifications  should  be  on  the  job  at  all  times  during  the  progress  of 
the  work.  He  should  be  a  man  of  broad  experience,  of  good  judg- 
ment, resourceful  and  tactful.  By  encouraging  honest,  experienced 
well  organized  paving  contractors,  by  providing  clear  well  drawn 
specifications,  calling  for  a  properly  designed  pavement,  by  securing 


86  LAYING  THE  BRICK 

dependable  inspection,  and  by  playing  fair  and  using  good  technical 
judgment  himself,  the  engineer  may  make  an  enviable  reputation  in 
the  building  of  durable  and  satisfactory  pavements.  After  all,  it  is 
the  strict  and  thoughtful  attention  given  to  the  minutest  details  of 
pavement  construction  which  frequently  makes  the  difference  between 
a  first  class  and  a  mediocre  piece  of  work. 


CHAPTER  VI 

PAVING  PROBLEMS 

HE  DESIGN  AND  CONSTRUCTION  of  pavements  has  developed 
under  the  rapidly  increasing  severity  of  traffic  into  a  special- 
ized science  calling  for  a  high  degree  of  technical  knowledge, 
a  large  fund  of  tact  and  good  judgment,  considerable  ex- 
perience, proper  organization  and  thorough  supervision.  Many 
problems  arise  on  every  job  which  must  be  solved  to  fit  particular 
conditions.  The  standardization  of  as  many  details  of  paving  con- 
struction as  possible  is  therefore  desirable  since  it  leaves  the  engi- 
neer more  time  to  apply  to  working  out  the  individual  problems  of 
each  piece  of  work.  This  chapter  is  therefore  devoted  to  a  discus- 
sion of  some  of  the  general  principles  of  highway  design  in  the  hope 
that  what  is  said  may  be  helpful  in  solving  some  of  these  individual 
problems  in  a  way  which  will  assure  the  best  service  and  the  most 
useful  and  beautiful  streets. 

A  source  of  much  contention  is  the  selection  of  the  type  of 
wearing  surface  for  streets  or  highways.  Enough  has  already  been 
said  condemning  the  practice  of  selecting  a  pavement  simply  because 
it  is  cheap.  Neither  should  a  good  material  be  placed  at  a  disad- 
vantage by  a  general  skimping  in  design  in  order  to  reduce  the  first 
cost.  Cheapness,  of  course,  is  a  desirable  attribute,  but  must  be 
considered  in  connection  with  the  life  and  maintenance  cost  of  the 
surfacing.  For  example  a  medium  traffic  business  street  is  to  be 
paved,  the  funds  to  be  provided  by  the  sale  of  bonds  drawing  4  per 
cent  interest  and  running  for  ten  years,  the  sinking  fund  to  retire 
the  bonds  drawing  3%  per  cent  interest.  If  the  street  is  paved  with 
3  inch  Vertical  Fiber  Brick  with  an  asphalt  filler  and  laid  on  a  6  inch 
depth  concrete  foundation,  the  computation  of  the  cost  per  square 
yard  per  year  over  a  period  of  40  years  would  be  made  as  follows: 
Assume  the  life  of  the  base  at  40  years  and  the  life  of  the  brick  sur- 
facing at  15  years.  The  cost  of  the  original  pavement  is  taken  at 
$2.00  per  square  yard  and  the  cost  of  renewing  the  entire  surface  at 
$1.40  per  square  yard.  Assume  that  the  street  is  kept  in  first  class 
repair  at  all  times  and  that  this  cost  for  the  brick  pavement  will  be 
2  cents  per  square  yard. 

Interest  on  first  bond  issue,  0.04x2.00x10 $0.8000 

Sinking  fund  first  bond  issue,   0.08524x2.00x10 1.7048 

Interest  on  second  bond  issue,   0.04x1.40x10 0.5600 

Sinking  fund  second  bond  issue,  0.08524x1.40x10..  1.1934 
Interest  on  third  bond  isssue,  0.04x1.40x10x2/3..  0.3733 
Sinking  fund  third  bond  issue,  0.08524x1.40x10x2/3  .7956 
Cost  of  repairs  0.02x40  8000 


Making  a  total  cost  for  40  years $6.2271 

or  cost  for  one  year  per  square  yard  $0.1557. 

Other      types      of     pavement     should      be      figured  in     the 

same  way  in  order  to  arrive  at    a    decision    in    regard    to  the    one 

factor  of  cheapness.    Attention  has  already  been  called  to  the  fact 


88 


PAVING  PROBLEMS 


that  considerations  other  than  cost,  however,  are  factors  in  the  se- 
lection of  a  suitable  pavement.  It  must  be  easy  to  maintain,  easy  to 
keep  clean,  sanitary,  have  a  low  tractive  resistance  and  yet  not  be 
slippery.  It  should  be  acceptable,  that  is,  the  personal  or  local 
preference  must  be  considered,  and  it  should  be  favorable  to  travel, 
that  is,  have  no  bad  effects  on  horses  or  vehicles  using  it.  All  of  these 
characteristics  are  not  equally  important  and  books  on  paving  usual- 
ly give  a  table  assigning  a  certain  weight  to  each  classification  for  an 
ideal  pavement.  They  do  not  usually  recognize,  however,  that  a 
characteristic  which  may  be  extremely  important  on  one  class  of 
street,  may  have  little  bearing  on  a  different  class  of  street.  The 
qualities  which  go  to  make  up  a  satisfactory  pavement  should  there- 
fore be  weighted  in  accordance  with  the  importance  of  each  quality 
on  the  particular  street  to  be  paved. 

The  following  table  gives  a  suggested  arrangement  for  three 
classes  of  highways  showing  an  ideal  standard  for  each  type  of 
highway  to  which  it  is  conceded  no  pavement  can  conform.  In  a 
parallel  column  is  shown  a  scoring  according  to  this  ideal  standard 
of  a  type  of  brick  pavement,  which  most  nearly  approaches  the  ideal. 

RELATIVE   VALUES  OF  DIFFERENT   QUALITIES    OF   PAVEMENT 


Class  '  A 

"  Streets 

Class  "B 

'  Street1- 

Class  "C 

'  Streets 

Ideal 

Brick 
Grouted 

Ideal 

Brick 
Asphalt 
Filler 

Idea] 

Brick 
Mono- 
lithic 

First  Cost   . 

10 

8 

12 

8 

15 

g 

Durability    (fre- 
quency of  repairs) 
Maintenance  cost  .   . 
Ease  of  Maintenance 
Low  Tractive 
Resistance  
Non-slipperiness    .    . 
Sanitation  

6 
20 

7 

15 
12 
10 

6 

18 

7 

14 
9 
9 

8 
15 
6 

7 
10 
15 

8 
15 
6 

6 
10 
13 

10 

22 
9 

16 

10 
5 

10 

22 
9 

15 

8 
5 

Noislessness 

7 

6 

10 

9 

4 

3 

Favorableness  .... 
Acceptability  

5 
8 

5 
6 

5 
12 

5 
10 

5 
5 

5 
5 

100 

87 

100 

90 

100 

90 

The  class  "A"  street  is  in  a  commercial  district  of  a  city  or 
town  subjected  to  heavy  hauling  and  mixed  traffic;  class  "B"  street 
is  in  the  built-up  residential  district  but  receives  some  through  traf- 
fic; class  "C"  street  is  a  main  traveled  country  road.  Other  types  of 
pavements  or  classes  of  streets  can  be  graded  in  the  same  way.  For 
example  on  the  class  A  street,  a  grading  for  a  macadam  pavement 
would  show  the  maximum  rate  for  first  cost  and  high  values  on  ease 
of  maintenance,  non-slipperiness,  and  noiselessness;  but,  on  the  other 
hand,  it  would  receive  minimum  values  for  durability  and  maintenance 
cost,  ease  of  cleaning,  sanitation,  and  acceptability,  which  would  put 
it  out  of  the  running. .  A  granite  block  pavement  would  receive  high 
values  for  durability  and  ease  of  maintenance,  but  would  be  rated 
low  in  first  cost  on  account  of  its  high  price  and  in  ease  of  cleaning, 
sanitation,  noiselessness,  and  favorableness.  To  properly  apply  such 
a  test  requires  a  large  fund  of  technical  knowledge  and  experience, 


PAVING  PROBLEMS  89 

but  in  any  case  such  a  table  is  only  an  aid  to  the  engineer  in  a  selec- 
tion of  the  best  type  of  pavement  for  all  the  conditions  which  must 
be  met  on  any  particular  street. 

The  rapid  development  of  modern  automobile  traffic  has  in- 
troduced conditions  wliich  have  proved  very  difficult  to  meet  in 
pavement  design.  In  the  first  place,  the  auto  truck  brings  loads  up- 
on the  pavement  which  are  many  times  greater  than  those  of  any  horse 
drawn  vehicle.  Eight  and  ten  ton  trucks  are  becoming  common  while 
some  trucks  approach  street  car  wheel  loads  in  magnitude.  The  street 
car  load  is  distributed  by  heavy  steel  rails  to  ties  which  distribute  it 
through  ballast  or  concrete  to  a  considerable  area  of  subgrade,  while 
the  truck  is  not  ccfnfined  in  its  travel  to  any  particular  street  or 
specially  designed  portion  of  the  pavement.  The  actual  load  on  an 
automobile  when  regulated  as  to  amount  and  width  of  tire,  by  reason- 
able laws,  is  not  so  serious  in  itself,  as  the  fact  that  the  load  is  mov- 
ing at  much  greater  speed  than  when  drawn  by  horses.  It  is  evident 
that  a  wheel  moving  at  a  slow  speed  will  roll  into  and  out  of  slight 
depressions  or  over  slight  humps,  but  when  a  certain  horizontal 
speed  is  attained,  it  will  drop  into  the  depression  or  off  the  hump, 
the  force  of  impact  multiplying  the  effect  of  the  load  depending  on 
the  height  of  the  drop.  It  is  the  impact  effect  of  these  heavy,  swiftly 
moving  loads,  which  is  the  most  destructive  to  pavements,  and  makes 
necessary  much  more  massive  foundations  in  order  to  absorb  the 
shocks  and  vibrations  and  more  careful  construction  than  the  actual 
increased  weight  of  the  loads  would  warrant.  Every  effort  must  be 
made  therefore  to  avoid  an  uneven  surface,  high  manhole  covers, 
valve  boxes  or  rails,  and  any  settlements  or  depressions  which  may 
appear,  must  be  corrected  immediately  in  order  to  prevent  as  much  as 
possible  the  destruction  of  the  adjacent  pavement  by  impact. 

The  pleasure  automobile  has  revolutionized  highway  construc- 
tion and  rendered  obsolete  several  types  of  road  construction.  An 
examination  of  what  takes  place  as  an  automobile  tire  moves  over 
the  road  surface  will  account  for  this.  In  the  first  place  instead  of 
being  drawn  over  the  road,  an  automobile  is  propelled  by  forces  ap- 
plied to  the  rear  wheels,  the  friction  between  the  tire  contact  surface 
and  the  road  surface  determining  the  amount  of  force  which  can  be 
applied  without  the  wheels  slipping  enough  to  simply  turn  without 
rolling  forward.  A  very  considerable  amount  of  slippage  however 
takes  place  even  when  the  vehicle  is  moving,  especially  when  the 
speed  is  being  accelerated  or  the  brakes  are  being  applied  and  in  ad- 
dition the  tires  are  constantly  exerting  a  continuous  push  or  pull  on 
the  pavement  surface.  As  the  portion  of  the  soft  rubber  tire,  which 
has  been  in  intimate  contact  with  the  road,  breaks  this  contact  there 
is  a  strong  suction  which  also  tends  to  displace  the  surfacing  ma- 
terial. 

The  pneumatic  tire  used  almost  exclusively  on  pleasure  auto- 
mobiles and  on  a  large  percentage  of  light  trucks  is  approximately 
circular  in  cross  section,  except  where  it  is  slightly  flattened  as  it 
rests  on  the  pavement.  Now  the  outside  edges  of  this  flattened  por- 
tion, (B.  Fig.  37)  lie  on  a  circumference  of  less  diameter  than  the 
center  point  (A.  Fig.  37)  and  consequently  travel  at  a  less  lineal 
velocity  since  the  center  point  must  travel  the  greatest  circumference 
and  therefore  at  the  greatest  speed  with  each  revolution  of  the  wheel. 
Without  considering  the  slippage  due  to  the  force  on  the  rear  wheels, 


90 


PAVING  PROBLEMS 


there  is,  therefore,  a  graduated  slipping  of  the  surface  of  the  tires  on 
all  the  wheels  in  contact  with  the  road  and  this  slipping  increases, 
the  greater  the  area  of  contact  or  the  flatter  the  tire.  It  is  especial- 
ly destructive  to  pavements  when  the  tire  settles  into  the  surface 
slightly  or  runs  in  a  longitudinal  depression  or  rut,  since  in  that  case 

a  greater  amount  of  the  cross 
sectional  circumference  of  the 
tire  is  in  contact  with  the  road 
surface  and  the  differences  in 
speed  of  the  extreme  sides  of 
the  tire  are  greater. 

These  three  factors,  first  the 
backward  push  given  the  road 
surface  by  the  propelling  force 
on  the  rear  wheels;  second  the 
suction  of  the  rubber  tire,  and 
third,  the  tire  slippage  due  both 
to  the  idriving  force  and  the 
different  lineal  velocities  of  the 
parts  of  the  tire  in  contact  with 
the  road,  have  caused  the  de- 
struction of  many  highway 
pavements  which  gave  satis- 
factory service  under  horse- 
drawn,  steel  tired  traffic.  Pave- 
ments, which  are  structurally 
strong  and  where  the  cohesion 
between  the  particles  compos- 
ing the  surface  is  sufficient  to 
withstand  these  displacing 
forces,  of  course  are  not  af- 
fected by  the  pneumatic  tire  ac- 
tion. Highway  pavements  suit- 
able for  the  traffic  of  Mac- 
adam's day  where  the  particles 
composing  the  wearing  surface 
are  weakly  bound  together,  are 
on  the  other  hand  rapidly  de- 
stroyed. Certain  other  types 
of  pavements  show  considerable 
wear  and  require  excessive 
maintenance  especially  in  the 
extreme  seasons  of  the  year 
when  the  cohesion  of  the  sur- 
Fig.  37 — Slip  of  Automobile  Tires.  face  is  likely  to  be  the  least. 

Street  design  and  especially  roadway  widths  have  received  con- 
siderable attention  from  engineers  recently,  and  the  large  number  of 
investigations  undertaken  have  furnished  valuable  data.  It  is  not 
proposed  to  enter  the  subject  of  city  planning  in  the  brief  space  of 
this  chapter,  but  a  word  in  regard  to  street  design  may  not  be  out  of 


PAVING  PROBLEMS 


91 


place.  It  seems  to  be  reasonable  and  economical  to  establish  the 
widths  of  paving  and  sidewalk  spaces  on  city  streets  to  adequately 
take  care  of  the  vehicular  and  pedestrian  traffic  which  the  street  in 
question  is  expected  to  develop,  but  to  provide  no  greater  or  no 
less  widths.  This  will  require  careful  study  of  the  amount  and  kind 
of  traffic,  whether  or  not  the  traffic  is  local  or  there  is  a  single 
or  double  street  car  track,  whether  the  property  abutting  will  be 
occupied  by  individual  residences,  apartment  houses,  retail  business 
or  warehouses,  and  a  number  of  other  factors.  It  has  been  found  that 
the  average  large  sized  automobile  or  loaded  wagon  has  a  width  of 
6^8  to  7  feet  and  that  an  auto  truck  or  transfer  wagon  with  the  horses 
turned  at  right  angles  to  the  wagon,  when  backed  against  the  curb, 


Fig-.    38 — The    Wide    Pavement    Spoils    This    Street. 


occupies  about  14  to  16  feet.  Double  street  car  tracks  are  almost 
always  laid  on  10  foot  centers,  so  that  including  safe  clearances  a 
single  track  car  line  would  require  about  11  feet  of  space  and  a 
double  car  track  about  21  feet.  (Where  the  vehicular  traffic  is  slow 
moving  the  allowable  clearance  may  be  less  and  an  8  foot  space  is 
sufficient  for  each  line  of  vehicles  to  be  provided  for,  but  where  speeds 
of  over  ten  miles  per  hour  are  allowed,  this  should  be  increased  to  9 
feet  and  on  boulevards  to  10  feet  for  safety.  Cars  standing  close  and 
parallel  to  the  curb  occupy  about  6%  feet  of  space  but  9  feet  must 


92 


PAVING  PROBLEMS 


be  provided  to  allow  for  clearance  on  both  sides.  When  they  are  al- 
lowed to  stop  at  an  angle  of  30  or  45  degrees  to  the  curb,  9  to  12  feet 
is  taken  up  and  12  to  15  feet  set  aside  for  safety.  These  figures  are 
average  results  of  a  great  many  actual  measurements  with  liberal 
allowances  for  clearances,  but  do  not,  of  course,  take  care  of  extreme 
cases.  These  are  so  unusual,  however,  that  an  occasional  wide  load 
will  not  cause  any  inconvenience  on  streets  where  the  above  spaces 
are  allowed. 


Fig.    39 — Vertical    Fiber    Brick    Pavement,    Garnett,    Kansas. 
A   Pleasing-  Treatment   of  a   Wide   Residence   Street. 

Take  for  example  a  retail  business  street  with  a  double  street 
car  track  and  where  automobiles  or  teams  are  likely  to  stand  along 
the  curb,  the  design  of  the  width  of  the  roadway  would  be  as  follows : 

Double  car  track   21  feet 

Vehicles  at  an  angle  along  each   curb    24  feet 

2  lines  of  vehicular  traffic    .18  feet 

63  feet 

On  a  semi  business  street  where  there  is  not  much  vehicular 
traffic  or  no  provision  is  made  for  a  line  of  standing  vehicles,  the 
width  could  be  reduced  24  feet,  making  it  39  feet.  Many  streets  with 
a  double  car  track  have  been  built  with  a  width  of  roadway  of  36 


PAVING  PROBLEMS  93 

feet  but  this  should  be  considered  the  minimum  for  that  class  of 
street.  On  a  street  in  the  wholesale  or  warehouse  district  where  the 
transfer  wagons  are  backed  against  the  curb  it  may  be  necessary  to 
provide  a  width  as  follows 

Line  of  wagons  backed  against  each  curb 30  feet 

Two  lines  of  slow  moving  traffic 16  feet 


46  feet 

Boulevards  ought  not  to  be  paved  of  less  width  than  is  suf- 
ficient to  provide  for  four  lines  of  swiftly  moving  automobiles  or  40 
feet.  On  the  average  residence  street  two  lines  of  traffic  of  9  feet 
each  and  one  standing  at  the  curb  of  8  feet,  or  a  total  width  of  26 
feet,  should  be  sufficient  for  all  purposes  as  this  will  allow  two  auto- 
mobiles to  pass  opposite  a  third  standing  at  the  curb  or  one  to  pass 
between  two  standing  at  opposite  curbs.  On  strictly  local  residence 
streets,  two  lines  of  traffic  width  will  prove  ample  or  a  roadway  width 
of  18  to  20  feet. 

The  ordinary  recommendation  for  roadway  widths  is  8  feet 
for  each  line  of  vehicles  and  10  feet  for  each  car  track.  The  widths 
given  above  are  made  liberal,  however,  to  provide  additional  clearance 
and  safety  in  driving  at  10  to  15  miles  per  hour.  It  should  be  noted 
that  these  widths  obtained  by  rational  design  are  frequently  in  odd 
numbers  and  not  the  usual  widths  found  in  cities,  where  pavements 
are  generally  a  certain  proportion  of  the  total  width  of  the  street 
without  regard  to  the  usefulness  of  such  roadway.  It  is  clearly 
not  good  engineering  to  provide  either  inadequate  or  extravagant 
roadways.  It  is  very  often  the  case  that  a  pavement  3  or  4  feet 
narrower  than  the  one  laid  would  serve  all  the  purposes  of  the  wider 
one,  or  an  additional  3  or  4  feet  to  a  pavement  on  a  busy  car  line 
street  would  provide  for  two  extra  lines  of  traffic.  Pavements  are 
expensive  to  lay  and  should  therefore  be  only  sufficient  to  provide  for 
traffic  needs  during  the  life  of  the  surfacing. 

On  country  roads,  the  problem  is  similar  except  that  one  track 
pavements  are  feasible  where  the  earth  shoulders  are  properly  main- 
tained for  turnouts  while  the  usual  maximum  amount  of  traffic  to  be 
provided  for  is  two  lines  of  swiftly  moving  vehicles.  For  a  single 
track  road  the  pavement  should  not  be  less  than  8  feet  nor  more  than 
10  or  11  feet.  The  best  width  is  10  feet,  a  narrower  pavement  requir- 
ing more  careful  driving  and  a  wider  one  providing  more  paving  than 
necessary  for  a  single  line  of  moving  vehicles.  Single  track  paved 
roads  should  be  built  at  one  side  of  the  center  line  as  a  half  of  a 
future  double  track  pavement.  The  storm  water  is  then  taken  di- 
rectly across  the  pavement  and  does  not  flow  from  the  pavement 
over  the  earth  road  which  is  on  only  one  side,  the  maintenance 
of  the  dirt  roadway  part  is  more  easily  handled  and  cheaper,  and  the 
pavement  can  be  satisfactorily  and  economically  widened  when  the 
amount  of  traffic  becomes  great  enough.  A  double  track  road  should 
not  be  less  than  18  feet  nor  more  than  22  feet  . 

The  amount  and  distribution  of  pavement  crowns,  that  is  the 
total  vertical  rise,  given  the  pavement  from  the  gutter  to  the  center 
of  the  roadway,  is  another  vexing  problem  in  pavement  design.  Many 
formulae  have  been  devised  for  solving  the  question  of  the  total 
amount  of  crown,  most  of  which  have  some  merit.  These  formulae 


PAVING  PROBLEMS  95 

of  course,  take  account  of  the  kind  of  pavement  and  the  width  of  road- 
way, and  some  vary  the  height  of  crown  with  the  percentage  of  grade 
on  the  street.  Some  kinds  of  pavements  being  smoother  and  wearing 
less  than  others,  will  shed  the  water  more  easily  and  quickly  and 
consequently  need  less  slope  from  the  center  toward  the  gutter. 
Pavements  which  are  subject  to  damage  or  washing  by  running  water 
should  have  a  maximum  slope  so  that  the  water  may  be  carried  to 
the  gutter  as  quickly  as  possible.  Less  crown  is  also  needed  on  hard 
surface  pavements  where  the  longitudinal  grade  of  the  street  is  steep 
than  where  it  is  flat.  A  formula  taking  account  of  all  these  factors 
is  too  complicated  for  practical  use.  In  order  to  promote  easy  riding 
qualities  pavement  crowns  should  be  as  flat  as  possible,  and  it  is 
recommended  that  a  rate  of  cross  fall  be  selected  for  each  type  of 
smooth  hard  surface  pavement,  which  will  be  satisfactory  for  flat 
grades  and  that  this  cross  fall  be  used  irrespective  of  the  longitudi- 
nal grade.  For  cement  grouted  brick  pavements  the  total  crown 
should  be  1/80  to  1/100  of  the  total  width  of  the  pavement,  and  for 
asphalt  filled  brick  1/60  to  1/80.  For  example  a  cement  grouted  brick 
pavement  40  feet  wide  would  have  a  crown  of  1/80  of  40  feet  or  0.5 
feet,  but  if  asphalt  filled,  the  crown  would  be  1/60  of  40  feet  or 
0.66  feet;  these  being  the  maximum  crowns  of  the  respective  types  of 
pavement.  If  there  is  a  car  track  in  the  street  the  space  between 
the  outside  rails  should  be  deducted  from  the  width  of  the  pavement 
before  applying  the  rule. 

Having  determined  the  amount  of  total  crown,  the  method  of 
distributing  this  fall  between  the  center  of  the  pavement  and  the 
gutter  must  be  worked  out.  The  simplest  way  of  course  would  be  to 
make  each  half  of  the  pavement  a  plane  surface,  but  this  is  open  to 
the  serious  objection  of  forming  an  ugly  ridge  in  the  center  and  not 
being  easy  riding.  The  usual  custom  is  for  the  transverse  section 
of  the  pavement  to  follow  a  parabola  in  form,  that  is  the  amount  of 
vertical  drop  below  the  center  at  any  point  is  proportional  to  the 
square  of  the  distance  from  the  center.  For  example  the  point  on 
the  pavement  y2  of  the  distance  from  the  center  to  the  gutter  would 
be  the  square  of  y2  or  %  of  the  total  crown  below  the  center;  at  % 
distant  from  the  center  the  pavement  would  be  1/16  of  the  total 
crown  below  the  center,  at  %  distant  it  would  be  9/16  and  so  on. 
The  objections  to  the  parabolic  form  of  pavement  surface  are  that 
it  makes  the  pavement  too  flat  in  the  central  section  and  too  steep 
on  the  sides,  does  not  drain  well  and  tends  to  drive  all  the  traffic 
toward  the  center.  It  is  seldom  used  nowadays  in  its  true  form  but 
is  more  or  less  modified  in  its  application.  A  curve  which  lies  be- 
tween the  parabola  and  the  straight  line  has  been  found  much  more 
practical.  This  is  a  hyperbola  and  is  represented  by  the  formula 
of  R.  S.  Beard. 

x2  =  cw«y  (m8-4)-mw«y«    (m  -  4)     , 

16  c2    (m  —  1) 

x=horizontal  distance  from  the  center, 
y=vertical  distance  from  top  of  crown, 
c=total  crown  of  the  street, 
w=width  of  pavement  between  curbs, 

rt 

—  =the  value  of  "y"  at  the  quarter  points. 


96 


PAVING  PROBLEMS 


By  selecting  values  of  "m",  the  shape  of  the  curve  may  be 
varied  at  will.  When  m  =  2,  the  equation  becomes  two  straight  lines, 
when  m  =  4,  the  equation  becomes  a  parabola. 

For  values  between  2  and  4  for  "m",  the  crown  curve  will  be 
an  hyperbola,  and  it  is  recommended  that  the  value  of  8/3  be  used 
as  this  gives  a  very  satisfactory  crown  curve.  The  formula  reduces 
then  to  ==  _5/—  V  49  -4-  1920  Xa  \ 

2         / 


>==  _— 


This  formula  gives  a  drop  of  approximately  %  of  the  total 
crown  at  a  point  one  quarter  of  the  distance  from  the  center  toward 
the  gutter,  %  drop  ac  a  point  one  half  the  distance  from  the  center 
to  the  curb,  that  is  at  the  "quarter  point,"  and  is  practically  a 
straight  line  from  this  point  to  the  gutter.  (Fig.  41)  Except  when 
templets  are  to  be  cut  for  use  on  wide  streets,  it  will  not  be  neces- 
sary to  compute  any  other  points  from  the  formula  as  the  above  rule 

sD//ference  between  af77ot/fjfofC,t/r& 
~  V  Jeff  exposed  and  fa  fa/ Crown. 


Fig.    41 — Comparison   of   Parabolic   and    Hyperbolic   Crown   Curves,    with 
Methods  of  Laying  Out  the  Latter. 

of  "Ys,  %  and  plane"  will  give  a  sufficient  number  of  points  to  finish 
the  pavement.  This,  however,  would  only  apply  where  the  curbs  on 
opposite  sides  are  level.  Where  the  curbs  are  at  different  eleva- 
tions, the  top  of  the  crown  curve  must  be  shifted  a  sufficient  dis- 
tance toward  the  side  of  the  high  curb  so  that  the  rise  from  the  low 
curb  does  not  exceed  the  maximum  allowed  for  that  class  of  pave- 
ment, and  then  the  crown  distributed  on  each  side  separately  as 
though  each  side  were  one  half  of  a  distinct  street.  For  example, 
if  a  street  40  feet  wide  is  to  be  paved  with  brick  and  the  curbs  are 
one  foot  lower  on  one  side  than  on  the  other,  the  crown  could  be 
shifted  ten  feet  off  center  or  30  feet  from  the  low  curb.  The  maxi- 
mum permissible  crown  from  the  low  curb  to  the  top  of  the  crown 
curve  would  then  be  1/60  of  60  feet,  treating  the  30  feet  toward  the 
low  curb  as  one  half  of  a  pavement  width,  or  1  foot,  and  the  mini- 
mum fall  from  the  top  of  the  crown  curve  toward  the  high  curb  would 
be  1/80  of  20  feet  or  1/4  foot,  making  a  difference  in  the  level  of 
the  pavement  at  opposite  curbs,  9  inches.  Starting  with  a  4  inch 
curb  face  on  the  low  side,  7  inches  of  curb  would  therefore  show 
above  the  pavement  on  the  high  side.  The  12  inch  crown  would  be 
distributed  in  the  30  feet  in  accordance  with  the  "%,  %  rule"  and  in 
like  manner  the  3  inch  crown  in  the  10  feet  toward  the  high  side. 
Where  the  difference  in  elevation  of  curbs  is  too  great,  it  may  be 


PAVING  PROBLEMS  97 

necessary  to  slope  the  pavement  on  a  plane  from  one  side  of  the 
street  to  the  other.  This  slope  should  not  exceed  a  rise  of  %  inch 
vertical  to  one  foot  horizontal,  the  balance  of  the  difference  if  there 
is  any,  being  taken  up  by  varying  the  exposure  on  the  curb.  The  sur- 
face of  the  pavement  should  not  come  higher  than  3  inches  below  the 
top  of  the  curb  and  that  high  only  when  not  much  storm  water  is  to 
be  carried;  neither  should  the  curb  face  above  the  pavement  be 
higher  than  ,12  inches  where  there  is  much  pedestrian  travel.  Greater 
differences  must  be  taken  care  of  by  a  stepped  curb  on  the  high  side 
or  what  is  called  double  or  triple  curb.  The  space  between  the 
curb  and  sidewalk  may  frequently  be  terraced  to  good  advantage 
where  there  is  no  necessity  for  the  walk  being  extended  out  to  the 
curb.  The  question  of  warped  pavement  surfaces  to  take  care  of 
unusual  conditions  such  as  have  just  been  noted  and  at  intersections 
often  requires  considerable  ingenuity  to  solve  satisfactorily. 

The  curbing  or  combined  curb  and  gutter  is  usually  construct- 
ed in  advance  of  the  paving  work,  but  it  is  in  some  ways  better  and 
more  economical  to  build  the  curb  at  the  same  time  and  as  a  unit 
with  the  concrete  foundation.  The  back  form  for  the  curbing  is  sub- 
stantially set  with  the  top  edge  true  to  the  line  and  grade  of  the  top 
of  the  curb  and  after  the  subgrade  has  been  trimmed  the  concrete 
foundation  is  placed  across  the  street  to  the  proper  thickness,  the 
templet  for  finishing  the  foundation  being  supported  from  the  top  of 
the  curb  forms.  After  this  concrete  has  begun  to  set  but  before  it 
becomes  hard,  the  face  form  for  the  curb  is  set  on  top  of  the  con- 
crete, spaced  and  clamped  to  the  rear  form  and  the  concrete  for  the 
curb  poured.  Special  steel  forms  are  on  the  market  which  carry 
the  face  form  suspended  from  the  rear  one  so  that  only  one  setting 
is  required,  and  the  concrete  can  be  poured  almost  at  one  time  or 
the  ordinary  wooden  face  board  may  be  suspended  by  spacers  and 
clamps  in  the  manner  shown  in  Fig.  42.  The  integral  curb  makes  a 
stronger,  more  solid  piece  of  construction  and  is  ordinarily  cheaper 
to  build,  but  requires  more  careful  workmanship  and  planning  in 
order  to  insure  a  satisfactorily  looking  job. 

The  radius  of  curvature  of  the  curbing  at  the  corners  depends 
on  the  width  of  pavement,  the  distance  from  the  curb  to  the  back  of 
the  sidewalk  and  the  kind  of  traffic  which  the  street  will  accommo- 
date. Narrow  pavements  should  have  larger  radii  on  the  corner 
curbs  than  is  necessary  for  wide  pavements,  but  the  radius  should 
not  be  greater  than  the  width  of  the  sidewalk  space  on  business 
streets.  Too  great  a  radius  of  curvature  encourages  fast  driving 
around  corners,  increases  the  width  of  intersection  pedestrians  must 
cross  and  cramps  the  sidewalk  space.  On  the  other  hand  a  sharp 
radius  seriously  impedes  vehicular  traffic  and  may  even  cause  a 
dangerous  condition  at  a  busy  intersection.  A  radius  of  12  to  18  feet 
is  ordinarily  sufficient  for  right  angle  corners  on  business  or  resi- 
dence streets  where  pedestrians  as  well  as  vehicular  traffic  must  be 
considered  and  where  the  pavement  is  wide  enough  for  at  last  three 
lines  of  traffic.  On  residence  streets  with  narrower  pavements  radii 
of  20  to  25  feet  might  be  used  while  on  parkways  or  boulevards 
accomodating  a  great  deal  of  motor  traffic  and  with  wide  parkings 
radii  of  20  to  50  feet  are  not  uncommon,  although  there  is  really  no 


98 


PAVING  PROBLEMS 


necessity  for  a  radius  greater  than  30  feet  on  any  right  angled  cor- 
ner. Turns  in  country  roads  are,  however,  eased  off  with  much 
longer  curves  with  a  minimum  radius  of  about  50  feet  and  running 
as  high  as  300  feet.  The  pavement  is  also  usually  widened  around 
corners  on  narrow  country  highways,  and  superelevated  'on  the 
outer  edge  in  proportion  to  the  sharpness  of  the  curves. 

Catch  basins  should  never  be  placed  in  the  center  of  the  radius, 
two  being  used  if  necessary  and  set  back  from  the  corner  away  from 
the  sidewalk  crossing.  If  this  is  done  the  pavement  may  frequently 

"$-&M/ 


face  form 
N   from  rear 

W^Tfyacerj 


To/a  of5/r?c/>  co/icrefe 


Back  form 


Fig-.   42 — Suspending-  Front   Curb   Form   for  Combined   Curb   and 
Foundation   Construction. 

be  gradually  warped  up  to  within  2  or  3  inches  of  the  top  of  the 
curb  around  the  radius,  draining  the  water  back  each  way  to  the  side 
basins  and  making  an  easy  step  for  pedestrians  crossing  the  street. 
It  is  also  a  good  plan  to  bring  the  pavement  flush  with  the  top  of  the 
curb  on  alley  returns  draining  the  water  toward  the  center  by  slight- 
ly dipping  the  pavement  and  thence  to  the  street  gutter.  This  avoids 
uncomfortable  steps  in  the  sidewalk.  Where  storm  water  sewers  and 
catch  basins  have  not  been  constructed,  the  problem  of  caring  for  the 
surface  drainage  of  the  pavements  becomes  more  difficult.  Valleys 
or  flat  gutters  in  the  pavement  surface  are  frequently  used  to  carry 
the  storm  water  across  intersections.  These  valleys  make  the  best 
of  a  bad  situation  but  even  where  they  are  wide  and  shallow  they 
spoil  the  easy  riding  qualities  of  the  pavement.  Another  method  is 
to  carry  the  water  under  the  intersection  in  a  concrete  box  or  in  an 
open  box  with  castiron  cover  plates,  but  these  are  not  usually  ef- 
ficient in  heavy  storms.  Catch  basins  may  also  be  constructed  and 
drained  into  a  pipe  laid  under  the  intersection  and  behind  the  curb 
on  the  other  side  to  an  outlet  through  the  curb  and  back  onto  the 


PAVING 


99 


pavement.  Where  the  street  has  a  grade  of  3  per  cent  or  over  this 
method  can  be  very  successfully  used  and  without  much  additional 
cost. 

The  space  between  the  curb  and  the  property  line  is  usually 
divided  except  on  business  streets,  into  a  parking  or  tree  planting 
space  and  a  sidewalk.  If  trees  are  to  be  planted  between  the  curb 
and  sidewalk  a  space  of  at  least  five  feet  and  preferably  seven  feet 
should  be  provided.  If  the  street  is  too  narrow  for  this,  the  trees 
should  be  planted  between  the  sidewalk  and  the  property  line. 
Sidewalks  ought  not  to  be  less  than  four  feet  in  width  as  this  will 
allow  a  person  to  pass  a  baby  carriage  without  stepping  off  the  walk. 
A  width  of  five  feet  will  allow  a  third  person  to  pass  two  others 
walking  abreast  and  is  a  good  average  for  the  majority  of  residence 
streets.  An  8  foot  sidewalk  is  customarily  used  on  boulevards.  In 
the  business  section  the  entire  space  between  the  curb  and  buildings 
is  usually  put  into  sidewalks,  and  from  8  to  20  foot  widths  are  the 
most  common.  Merchants  usually  object  to  a  greater  width  than 
about  20  feet  as  it  throws  the  vehicular  traffic  too  far  from  their  dis- 
play windows  and  of  course  is  not  necessary  from  the  pedestrian 
standpoint.  We  might,  however,  learn  something  from  the  treat- 
ment of  some  of  the  wide  business  streets  in  Europe,  which  are  fre- 
quently lined  with  trees  and  where  cafe  patrons  are  served  under 
awnings  at  tables  set  on  the  wide  sidewalks.  It  is  more  difficult  to 
plan  the  improvements  for  a  street  which  is  much  wider  than  is 
needed  to  make  ample  allowances  for  present  use,  than  it  is  to  plan 
a  street  which  is  too  narrow.  American  engineers  seem  to  have 
been  particularly  devoid  of  any  new  ideas  in  street  planning,  a  sub- 
ject which  offers  opportunities  for  first  class  engineering  work. 

On  residence  streets  which  have  been  platted  at  extravagant 
widths,  ample  tree  planting  space  should  be  provided  for  one  or  two 
rows  of  trees  between  the  curbing  and  the  sidewalk  and  the  balance 
of  the  sidewalk  space  not  occupied  by  the  sidewalk  itself  thrown  into 
a  grass  or  shrubbery  space  between  the  sidewalk  and  property  line. 
In  fact,  even  on  narrrow  streets  it  is  a  disadvantage  to  locate  the 
edge  of  the  sidewalk  on  the  property  line.  Once  widths  of  pavements 
and  sidewalks  sufficient  to  provide  for  vehicular  and  pedestrian  traf- 
fic have  been  determined  upon,  the  balance  of  the  width  of  residence 
streets  should  be  devoted  to  lawn,  shrub  and  tree  planting  spaces  as 
these  are  much  more  restful  and  pleasing  to  the  eye  than  any  pave- 
ment or  sidewalk. 

The  discussion  of  the  minor  details  in  pavement  construction 
and  street  planning  could  be  continued  at  considerable  length  but  it 
is  hoped  that  enough  has  been  said  to  show  the  possibilities  of  care- 
ful street  design  and  construction  from  both  a  practical  and 
aesthetic  standpoint.  The  pavement  is  the  utilitarian  part  of  the 
street  and  should  be  constructed  in  all  details  in  the  manner  which 
will  best  serve  at  the  lowest  ultimate  cost  all  the  purposes  for  which 
it  will  be  used.  There  is  an  opportunity  along  these  lines  for  much 
improvement  in  the  ordinary  American  practice. 


' 


APPENDIX 


STANDARD  SPECIFICATIONS 

FOR  VITRIFIED  BRICK 

PAVEMENTS. 

H  E  S  E  specifications,  developed  by  the 
Western  Paving  Brick  Manufacturers'  Asso- 
ciation, through  a  painstaking  study  of  the 
manufacturing  and  constructional  problems  involved, 
are  accurate  and  comprehensive  in  their  language 
and  stipulations,  and  are  promulgated  in  the  interests 
of  the  best  and  most  economical  construction  of 
permanent  street  and  road  improvements.  It  is 
hoped  that  the  general  public  may  profit  consider- 
ably by  this  educational  effort.  Engineers,  City 
Councils,  and  City  or  County  Commissioners,  or 
others  interested  in  permanent  road  construction, 
are  invited  to  use  these  specifications  in  whole  or  in 
part  whenever  it  appears  to  their  interest  to  do  so. 
Copies  may  be  obtained  gratis  by  applying  to  the 
Secretary  of  the  Association,  G.  W.  Thurston, 
416  Dwight  Building,  Kansas  City,  Missouri 


SPECIFICATIONS 


MATERIALS  FOR  BRICK  PAVEMENT 


PORTLAND  CEMENT.  The  cement  shall  be  packed  in  strong 
cloth  or  canvas  sacks.  Each  package  shall  have  printed  upon  it  the 
brand  and  the  name  of  the  manufacturer.  Packages  received  in 
broken  or  damaged  condition  may  be  rejected  or  accepted  as  fractional 
packages,  at  the  option  of  the  Engineer. 

Four  (4)  bags  shall  constitute  a  barrel,  and  the  average  net 
weight  of  the  cement  contained  in  one  bag  shall  not  be  less  than 
ninety-four  (94)  pounds,  or  three  hundred  and  seventy-six  (376) 
pounds  net  per  barrel.  The  weights  of  the  separate  packages  shall 
be  uniform. 

Cement  failing  to  meet  the  seven  (7)  day  requirement  may  be 
held  to  await  the  twenty-eighth  (28)  day  test  before  rejecting. 

Samples  shall  be  taken  at  random  from  sound  packages,  and 
the  cement  from  each  package  shall  be  tested  separately.  The  ac- 
ceptance or  rejection  shall  be  based  on  the  following  requirements: 

The  term  "Portland  Cement"  by  the  terms  of  this  contract  is 
applied  to  the  product  obtained  by  finely  pulverizing  clinker  produced 
by  calcining  to  incipient  fusion  an  intimate  and  properly  proportioned 
mixture  of  argillaceous  and  calcareous  materials,  with  no  additions 
subsequent  to  calcination  excepting  water  and  calcined  or  uncalcined 
gypsum. 

The  specific  gravity  of  the  cement,  thoroughly  dried  at  100  de- 
grees centigrade,  shall  not  be  less  than  3.10. 

It  shall  leave  by  weight  a  residue  of  not  more  than  22%  on  the 
standard  No.  200  sieve. 

If  shall  not  develop  initial  set  in  less  than  45  minutes  when  the 
Vicat  needle  is  used,  or  60  minutes  when  the  Gillmore  needle  is  used. 
Final  set  shall  be  attained  within  10  hours. 


104  SPECIFICATIONS 

The  average  tensile  strength  in  pounds  per  square  inch  of  not 
less  than  three  standard  mortar  briquettes  composed  of  one  part 
'cement  and  three  parts  standard  sand,  by  weight,  shall  be  equal  to  or 
higher  than  the  following:  — 

Age.                                                                                  Strength. 
7  days  (1  day  in  moist  air,    6  days  in  water) 200  Ibs. 

28  days  (1  day  in  moist  air,,27  days  in  water) 300  Ibs. 

The  average  tensile  strength  of  standard  mortar  at  28  days 
shall  be  higher  than  the  strength  at  7  days. 

Pats  of  neat  cement  about  three  (3)  inches  in  diameter,  one- 
half  CVz\  inch  thick  at  the  center  and  tapering  to  a  thin  edge,  shall 
be  kept  in  moist  air  for  a  period  of  24  hours. 

They  shall  then  be  exposed  in  any  convenient  way  in  an  at- 
mosphere of  steam,  above  boiling  water,  in  a  loosely  closed  vessel 
for  a  period  of  five  (5)  hours. 

These  pats,  to  satisfactorily  pass  the  requirements,  shall  remain 
firm  and  hard  and  show  no  signs  of  distortion,  checking,  cracking 
or  disintegration. 

The  following  limits  shall  not  be  exceeded: 

Loss  on  ignition,  4.00%.  Insoluble  residue  0.85%.  -Sulfuric 
Anhydride  (SO3)  2.00%.  Magnesia  (MgO)  5.00%. 

All  tests  shall  be  made  in  accordance  with  the  standards  adopted 
by  the  American  Society  for  Testing  Materials,  January  1,  1917. 

FINE  AGGREGATE.  All  sand  shall  be  clean  and  free  from 
lumps  of  clay,  sticks  or  organic  matter,  and  contain  not  more  than 
5%  of  silt  or  loam.  It  shall  be  passed  upon  by  the  Engineer  as 
suitable  for  the  purpose  for  which  it  is  intended  to  be  used. 

Sand  for  concrete  and  cement-sand  bed  shall  be  sharp  and 
coarse  or  a  mixture  of  fine  and  coarse  grains  with  the  coarse  grains 
predominating.  It  shall  all  pass  when  dry  a  screen  having  4  meshes 
to  the  lineal  inch.  The  sand  for  the  cement  grout  shall  be  screened 
of  all  sizes  retained  on  a  screen  having  10  meshes  to  the  lineal  inch, 
uniformly  graded  and  composed  of  sharp,  angular  grains.  Bri- 
quettes made  of  the  sand  for  concrete  or  grout  in  the  proportion  of 
one  part  Portland  cement  to  three  parts  sand  shall  not  show  less 
tensile  strength  at  7  and  28  days  than  briquettes  made  at  the  same 
time  with  the  same  cement  but  using  Standard  Ottawa  sand.  Broken 
stone  chips  or  gravel  answering  the  above  specifications  may  be  used 
as  sand  if  approved  by  the  Engineer. 

COARSE  AGGREGATE.  The  broken  stone  or  gravel  shall  be 
clean,  sound,  and  durable,  free  from  dust,  dirt,  shale,  rotten  or 
disintegrated  rock,  or  foreign  matter.  Gravel  encrusted  with  sand 
grains  or  dirt  will  not  be  allowed.  The  broken  stone  or  gravel  must 
be  screened  of  all  sizes,  passing  a  screen  having  4  meshes  to  the  lineal 
inch  and  retained  on  a  screen  having  openings  2  inches  in  diameter, 
except  that  where  the  concrete  foundation  is  5  inches  or  more  in 
thickness,  the  largest  piece  shall  pass  a  ring  2%  inches  in  diameter. 
It  shall  grade  uniformly  from  the  smallest  to  the  largest  size.  Flint 
"chats,"  is  used,  shall  be  screened,  clean,  coarse,  and  angular. 

DELIVERY  OF  MATERIAL  FOR  FOUNDATION.  All  cement 
shall  be  delivered  on  platforms  held  at  least  6  inches  off  the  ground 


SPECIFICATIONS  105 

and  protected  by  tarpaulins  from  the  elements.  Fine  and  coarse 
aggregate  may  be  delivered  on  the  rolled  subgrade  if  dry  and  com- 
pact, but  in  wet  weather  or  where  the  subgrade  is  cut  up,  the  En- 
gineer may  require  them  to  be  delivered  on  tight  plank  platforms  or 
on  the  pavement  of  intersecting  streets. 

WATER.     The  water  shall  be  clean,  free  from  oil,  acid,  alkali 
or  vegetable  matter. 


THE  BRICK 

All  brick  must  be  No.  1  pavers  of  the  sizes  or  types  commer- 
cially known  as  "Vertical  Fiber  Brick,"  "Repressed  Block,"  "Wire- 
Cut-Lug  Block"  or  "Brick,"  whichever  kind  may  be  specified  for  use. 
They  must  be  thoroughly  annealed,  tough  and  durable,  regular  in 
size,  and  evenly  burned.  When  broken,  they  shall  show  a  dense, 
stone-like  body,  free  from  lime,  large  air  pockets,  marked  laminations 
or  cracks  which  would  tend  to  weaken  the  structure. 

The  size  of  Vertical  Fiber  Brick  shall  not  be  less  than  three 
and  three-quarters  (3%)  inches  nor  more  than  four  and  one-half 
(4%)  inches  in  width  excluding  lugs,  and  shall  not  be  less  than 

inches*  in  depth;  the  size  of  Repressed 

Block  shall  not  be  tess  than  three  (3)  inches  nor  more  than  three 
and  three-quarter  (3%)  inches  in  width  excluding  lugs,  and  not  less 
than  four  (4)  inches  in  depth;  the  size  of  Wire  Cut  Lug  Block  'shall 
not  be  less  than  three  and  one-quarter  (31/4)  inches  nor  more  than 
three  and  three-quarter  (3%)  inches  in  width  excluding  lugs,  and 

not  less  than inches*   in  depth;    the  size 

of  Brick  shall  not  be  less  than  two  (2)  inches  nor  more  than  two  and 
one-half  (2%)  inches  in  width  excluding  lugs,  and  not  less  than 
four  (4)  inches  in  depth. 

All  brick  and  block  shall  not  be  less  than  eight  (8)  inches  nor 
more  than  nine  (9)  inches  in  length.  The  brick  or  block  from  any 
one  plant  shall  not  vary  more  than  one-eighth  (%)  inch  in  width 
from  the  average  or  standard  size  of  its  product,  nor  more  than  % 
inch  in  depth  from  that  specified. 

If  the  edges  of  the  brick  are  rounded,  the  radius  shall  not  exceed 
three-sixteenths  (3/16)  of  an  inch.  Brick  laid  so  that  any  kiln 
marks  will  show  on  the  surface  of  the  finished  pavement  shall  be 
rejected  if  the  kiln  marks  exceed  one-fourth  (*4)  of  an  inch  in  depth; 
and  at  least  one  edge  shall  show  but  slight  kiln  marks. 

".Vertical  Fiber  Brick  may  be  varied  in  depth  from  two 
and  one-half  (2^)  inches  to  four  (4)  inches  and  Wire-Cut-Lug  Block 
may  be  varied  in  depth  from  three  (3)  inches  to  four  (4)  inches,  and 
the  proper  depth  should  be  inserted  in  the  blank  space. 

For  light  traffic  residence  streets  and  for  moderate  traffic 
country  roads  of  the  monolithic  type  it  is  recommended  that  a  2l/fa 
inch  .depth  be  used;  for  business  streets  in  towns  and  small  cities 
and  other  streets  of  moderately  heavy  traffic  and  on  the  main  traveled 
country  roads  that  a  three  (3)  inch  depth  brick  be  used;  and  for  heavy 
traffic  business  streets  in  large  cities  a  four  (4)  inch  depth  brick  be 
used. 


106  SPECIFICATIONS 

(a)  Only  brick  with   raised   lugs   on  one   side   not  to   exceed 
one-quarter  (^4)  of  an  inch  in  height  shall  be  used.* 

(b)  Only   Vertical    Fiber   Brick   without   raised   lugs   shall   be 
used.* 

*Either  clause  (a)  or  (b)  should  be  crossed  out.  The 
lug-less  type  of  Vertical  Fiber  pavement  is  recommended  where  asphalt 
filler  is  used  and  an  especially  smooth  even  wearing-  surface  is  desired. 
It  is  slig-htly  more  expensive  than  where  lug's  are  used  on  account  of 
the  greater  number  of  brick  per  square  yard  being  used. 

NOTE:  Where  the  word  "brick"  is  used  in  these  specifications 
it  is  Intended  to  refer  to  Vertical  Fiber  Brick,  Brick  Block,  Wire-Cut- 
I.IIK  Block  or  Brick,  whichever  may  be  specified. 


RATTLER  TEST  FOR  BRICK 


THE  CONSTRUCTION  OF  THE  RATTLER 

General  Design.  The  machine  shall  be  of  good  mechanical 
construction,  self-contained,  and  shall  conform  to  the  following  de- 
tails of  material  and  dimensions,  and  shall  consist  of  barrel,  frame, 
and  driving  mechanism  as  herein  described. 

The  Barrel.  The  barrel  of  the  machine  shall  be  made  up  of 
the  heads,  headliners,  staves  and  stave-liners. 

The  heads  may  be  cast  in  one  piece  with  the  trunnions,  which 
shall  be  2%  in.  in  diameter,  and  shall  have  a  bearing  6  in.  in  length, 
or  they  may  be  cast  with  heavy  hubs,  which  shall  be  bored  out 
for  2  7/16  in.  shafts,  and  shall  be  keyseated  for  two  keys,  each  y2 
by  %  in.  and  spaced  90  degrees  apart.  The  shaft  shall  be  a  snug 
fit  and  when  keyed  shall  be  entirely  free  from  lost  motion.  The 
distance  from  the  end  of  the  shaft  or  trunnion  to  the  inside  face 
of  the  head  shall  be  15%  in.  in  the  head  for  the  driving  end  of  the 
rattler,  and  11%  in.  for  the  other  head,  and  the  distance  from  the 
face  of  the  hubs  to  the  inside  face  of  the  heads  shall  be  5^  in. 

The  heads  shall  be  not  less  than  %  in.  thick,  nor  more  than 
%  in.  thick.  In  outline,  each  head  shall  be  a  regular  14-sided 
polygon  inscribed  in  a  circle  28%  in.  in  diameter.  Each  head 
shall  be  provided  with  flanges  not  less  than  %  in.  thick  and  extend- 
ing outward  2y2  in.  from  the  inside  face  of  the  head  to  afford  a 
means  of  fastening  the  staves.  The  surface  of  the  flanges  of  the 
head  shall  be  smooth  and  give  a  true  and  uniform  bearing  for  the 
staves.  To  secure  the  desired  true  and  uniform  bearing  the  sur- 
faces of  the  flanges  of  the  head  shall  be  either  ground  or  machined. 
The  flanges  shall  be  slotted  on  the  outer  edge,  so  as  to  provide  for 
two  %  in.  bolts  at  each  end  of  each  stave,  said  slots  to  be  13/16  in. 
wide  and  2%  in.,  center  to  center.  Each  slot  shall  be  provided 
with  a  recess  for  the  bolt  head,  which  shall  act  to  prevent  the  turn- 
ing of  the  same.  Between  each  two  slots  there  shall  be  a  brace 
%  in.  thick,  extending  down  the  outward  side  of  the  head  not  less 
than  2  in. 


SPECIFICATIONS  107 

There  shall  be  for  each  head  a  cast-iron  headliner  1  in.  in 
thickness  and  conforming  to  the  outline  of  the  head,  but  inscribed 
in  a  circle  28 V8  in.  in  diameter.  This  headliner  shall  be  fastened  to 
the  head  by  seven  %  in.  cap-screws,  through  the  head  from  the 
outside.  Whenever  these  headliners  become  worn  down  y2  inch 
below  their  initial  surface  level  at  any  point  of  their  surface,  they 
shall  be  replaced  with  new  ones.  The  metal  of  these  headliners 
shall  be  hard  machinery  iron  and  should  contain  not  less  than  one 
per  cent  of  combined  carbon. 

The  staves  shall  be  made  of  6-in.  medium-steel  structural 
channels,  27%  in.  long  and  weighing  15.5  Ib.  per  lineal  foot.  The 
staves  shall  have  two  holes  13/16  in.  in  diameter,  drilled  in  each 
end,  the  center  line  of  the  holes  being  1  in.  from  the  end  and  1% 
in.  either  way  from  the  longitudinal  center  line.  The  spaces  be- 
tween the  staves  shall  be  as  uniform  as  practicable,  but  shall  not 
exceed  5/16  in. 

The  interior  or  flat  side  of  each  stave  shall  be  protected  by  a 
liner  %  in.  thick  by  5^  in.  wide  by  19%  in.  long.  The  liner  shall 
consist  of  medium-steel  plate,  and  shall  be  riveted  to  the  channel 
by  three  %  in.  rivets,  one  of  which  shall  be  on  the  center  line  both 
ways  and  the  other  two  on  the  longitudinal  center  line  and  spaced 
7  in.  from  the  center  each  way.  The  rivet  holes  shall  be  counter- 
sunk on  the  face  of  the  liner  and  the  rivets  shall  be  driven  hot  and 
chipped  off  flush  with  the  surface  of  the  liners.  These  liners  shall 
be  inspected  from  time  to  time,  and  if  found  loose  shall  be  at  once 
re-riveted. 

Any  test  at  the  expiration  of  which  a  stave-liner  is  found 
detached  from  the  stave  or  seriously  out  of  position  shall  be  re- 
jected. When  a  new  rattler,  in  which  a  complete  set  of  new  staves 
is  furnished,  is  first  put  into  operation,  it  shall  be  charged  with  400 
Ib.  of  shot  of  the  same  sizes,  and  in  the  same  proportions  as  pro- 
vided in  standard  charge,  and  shall  then  be  run  for  18,000  revolu- 
tions at  the  usual  prescribed  rate  of  speed.  The  shot  shall  then  be 
removed  and  a  standard  shot  charge  inserted,  after  which  the  rattler 
may  be  charged  with  brick  for  a  test. 

No  stave  shall  be  used  for  more  than  70  consecutive  tests 
without  renewing  its  lining.  Two  of  the  14  staves  shall  be  removed 
and  relined  at  a  time  in  such  a  way  that  of  each  pair,  one  falls 
upon  one  side  of  the  barrel  and  the  other  upon  the  opposite  side, 
and  also  so  that  the  staves  changed  shall  be  consecutive  but  not 
contiguous;  for  example,  1  and  8,  3  and  10,  5  and  12,  7  and  14, 
2  and  9,  4  and  11,  6  and  13,  etc.  to  the  end  that  the  interior  of  the 
barrel  at  all  times  shall  present  the  same  relative  condition  of  re- 
pair. The  changes  in  the  staves  should  be  made  at  the  time  when 
the  shot  charges  are  being  corrected,  and  the  record  must  show  the 
number  of  charges  run  since  the  last  pair  of  new  lined  staves  was 
placed  in  position. 

The  staves  when  bolted  to  the  heads  shall  form  a  barrel  20  in. 
long,  inside  measurement,  between  headliners.  The  liners  of  the 
staves  shall  be  so  placed  as  to  drop  between  the  headliners.  The 
staves  shall  be  bolted  tightly  to  the  heads  by  four  %-in.  bolts,  and 
each  bolt  shall  be  provided  with  a  lock  nut,  and  shall  be  inspected 


108  SPECIFICATIONS 

at  not  less  frequent  intervals  than  every  fifth  test  and  all  nuts 
kept  tight.  A  record  shall  be  made  after  each  inspection  showing 
in  what  condition  the  bolts  were  fonnd. 

The  Frame  and  Driving  Mechanism.  The  barrel  shall  be 
mounted  on  a  cast-iron  frame  of  sufficient  strength  and  rigidity  to 
support  it  without  undue  vibration.  It  shall  rest  on  rigid  founda- 
tion with  or  without  the  interposition  of  wooden  plates,  and  shall 
be  fastened  thereto  by  bolts  at  not  less  than  four  points. 

It  shall  be  driven  by  gearing  whose  ratio  of  driver  to  driven 
is  not  less  than  one  to  four.  The  counter  shaft  upon  which  the 
driving  pinion  is  mounted  shall  not  be  less  than  1  15/16  in.  in  dia- 
meter, with  bearing  not  less  than  6  in.  in  length.  If  a  belt  drive  is 
used  the  pulley  shall  not  be  less  than  18  in.  in  diameter  and  §V%  in. 
in  face.  A  belt  at  least  6  in.  in  width  properly  adjusted,  to  avoid  un- 
necessary slipping,  should  be  used. 

The  Abrasive  Charge.  The  abrasive  charge  shall  consist  of 
cast-iron  spheres  of  two  sizes.  When  new,  the  larger  spheres  shall 
be  3.75  in.  in  diameter  and  shall  weigh  approximately  7.  '5  Ib.  (3.40 
kg.)  each.  Ten  spheres  of  this  size  shall  be  used. 

These  shall  be  weighed  separately  after  each  ten  tests,  and  if 
the  weight  of  any  large  sphere  falls  to  7  Ib.  (3.175  kg.)  it  shall  be 
discarded  and  a  new  one  substituted;  provided,  however,  that  all 
of  the  large  spheres  shall  not  be  discarded  and  substituted  by  new 
ones  at  any  single  time,  and  that  so  far  as  possible  the  large  spheres 
shall  compose  a  graduated  series  in  various  stages  of  wear. 

When  new,  the  smaller  spheres  shall  be  1.875  in.  in  diameter 
and  shall  weigh  approximately  0.%  Ib.  (0.43  kg.)  each.  In  general, 
the  number  of  small  spheres  in  a  charge  shall  not  fall  below  245  nor 
exceed  260.  The  collective  weight  of  the  large  and  small  spheres 
shall  be  as  nearly  300  Ib.  as  possible.  No  small  sphere  shall  be 
retained  in  use  after  it  has  been  worn  down  so  that  it  will  pass  a 
circular  hole  1.75  in.  in  diameter  drilled  in  an  iron  plate  y±  in.  in 
thickness,  or  weigh  less  than  0.75  Ib.  (0.34  kg.).  Further,  the  small 
spheres  shall  be  tested,  by  passing  them  over  the  above  plate  or 
by  weighing,  after  every  ten  tests,  and  any  which  pass  through  or 
fall  below  the  specified  weight,  shall  be  replaced  by  new  spheres; 
provided,  further,  that  all  of  the  small  spheres  shall  not  be  rejected 
and  replaced  by  new  ones  at  any  one  time,  and  that  so  far  as  possible 
the  small  spheres  shall  compose  a  graduated  series  in  various 
stages  of  wear.  At  any  time  that  any  sphere  is  found  to  be  broken 
or  defective  it  shall  at  once  be  replaced. 

The  iron  composing  these  spheres  shall  have  a  chemical  com- 
position within  the  following  limits: 

Combined    carbon     not  under  2.50  per  cent 

Graphitic    carbon     "       over     0.25 

Silicon    "  1.00 

Manganese "         "         0.50         " 

Phosphorus "         "         0.25 

Sulfur  .  .   "  0.08 


SPECIFICATIONS  109 

For  each  new  batch  of  spheres  used,  the  chemical  analysis 
shall  be  furnished  by  the  maker  or  be  obtained  by  the  user,  before 
introducing  into  the  charge,  and  unless  the  analysis  meets  the  above 
specifications,  the  batch  of  spheres  shall  be  rejected. 

SELECTION  OF  SAMPLES  FOR  TESTING.  Samples  of  brick 
of  uniform  shape  and  appearance  shall  be  taken  by  the  Engineer 
when  deemed  expedient.  Bricks  having  a  defect  that  would  cull 
them  shall  not  be  used. 

DELIVERY  OF  BRICK.  The  contractor  shall  notify  the  proper 
official  of  the  location  and  car  number  of  each  carload  of  brick 
received,  so  that  samples,  if  deemed  necessary  and  if  the  brick 
have  not  been  tested  at  the  plant,  may  be  taken  and  tested  by  the 
Engineer,  and  no  brick  shall  be  delivered  on  or  adjacent  to  any 
improvement  on  which  brick  are  to  be  used  until  a  written  state- 
ment has  been  received  from  the  Engineer  or  his  authorized  repre- 
sentative, that  they  have  been  superficially  inspected  or  have  passed 
the  required  tests.  Decision  relative  to  each  carload  will  be  made 
within  twenty-four  (24)  hours  of  notice. 

A  certificate  of  acceptance  of  the  brick  on  the  rattler  test  will 
not  waive  the  right  to  reject  individual  brick  on  the  street  which 
fail  to  meet  the  requirements  of  these  specifications,  other  than  the 
rattler  test. 

Whenever  possible  the  brick  will  be  tested  at  the  manufacturing 
plant  before  loading  into  cars.  When  brick  are  not  tested  at  the 
plant,  any  tests  desired  shall  be  made  before  cars  are  unloaded  at 
destination.  When  tested  from  the  kiln,  samples  shall  be  taken  from 
different  locations  in  the  kiln  where  in  the  opinion  of  the  engineer 
or  his  representative,  there  is  a  variation  in  the  quality  of  the  brick, 
but  at  least  one  test  shall  be  made  on  each  15,000  brick. 

NUMBER  OF  BRICK  IN  EACH  TEST.  Ten  paving  brick 
shall  constitute  the  number  to  be  used  in  a  single  test.  The  brick 
shall  be  thoroughly  dried  before  testing. 

THE  TEST.  The  sample  of  the  brick  selected  for  test  shall 
be  placed  in  the  rattler  hereinbefore  described.  The  rattler  shall 
be  rotated  at  a  rate  of  not  less  than  '29%  not  more  than  30%  revo- 
lutions per  minute,  and  1,800  revolutions  shall  constitute  the  stan- 
dard test.  A  counting  machine  shall  be  attached  to  the  rattler  for 
counting  the  revolutions. 

A  margin  of  not  to  exceed  ten  (10)  revolutions  will  be  allowed 
for  stopping.  In  case  a  charge  is  allowed  to  run  several  minutes 
beyond  it's  proper  termination,  and  the  loss  incurred  is  still  within 
the  prescribed  limits,  then  the  test  shall  not  be  discarded,  but  the 
fact  shall  be  entered  on  the  record. 

STOPPING  AND  STARTING.  Only  one  (1)  start  and  stop 
per  test  is  regular  and  acceptable.  If  from  accidental  causes  a  test 
is  stopped  and  started  twice  extra,  and  the  loss  exceeds  the  maxi- 
mum permissible,  the  test  shall  be  disqualified  and  another  made. 


110  SPECIFICATIONS 

ABRASION  LOSS.  The  loss  shall  be  calculated  in  percentage 
of  the  original  weight  of  the  dried  brick  composing  the  charge. 
In  weighing  the  rattled  brick,  any  piece  weighing  less  than  one  (1) 
pound  shall  be  rejected.  The  brick  shall  not  lose  of  their  weight 

more   than    (....%)*    per   cent 

when  submitted  to  the  above  described  test. 

THE  RECORD 

DESCRIPTION.  The  operator  shall  keep  an  official  book  in 
which  the  alternate  pages  are  perforated  for  removal.  The  records 
shall  be  kept  in  duplicate,  by  use  of  a  carbon  paper  between  the 
first  and  second  sheets,  and  when  all  entries  are  made  and  calcu- 
lations are  completed,  the  original  record  shall  be  removed  and  the 
carbon  duplicate  preserved  in  the  book.  All  calcualtions  must  be 
made  in  the  space  left  for  that  purpose  in  the  record  blank,  and  the 
actual  figures  must  appear.  The  record  must  bear  its  serial  number 
and  be  filled  out  completely  for  each  test  and  all  data  as  to  dates 
of  inspections,  weighing  of  shot,  and  replacement  of  wornout  parts 
must  be  carefully  entered,  so  that  the  records  remaining  in  the  book 
constitute  a  continuous  one.  In  event  of  further  copies  of  a  record 
being  needed,  they  may  be  furnished  on  separate  sheets,  but  in  no 
case  shall  the  original  carbon  copy  be  removed  from  the  record  book. 

The  blank  form  for  all  official  brick  tests  is  given  on  the  op- 
posite page. 

*Care  must  be  taken  in  specifying  the  percentage  of  abrasion  loss  to 
allow  for  the  size  of  the  brick  and  for  brick  with  square  edges  like  the  Vertical  Fiber 
and  the  Wire-Cut-Lug  Brick.  A  round  cornered  brick  will  stand  from  2  to  3  per  cent 
better  rattler  test  than  a  brick  of  the  same  size  and  quality  but  having  square  edges. 
A  small  sized  brick  also  has  a  larger  proportion  of  edges  to  its  weight  than  a  larger 
sized  brick  and  is  more  likely  to  be  broken  in  the  rattler.  The  following  percentages 
of  loss  are  recommended  for  the  various  classes  of  brick: 

Four  inch  Vertical  Fiber  or  Wire-Cut-Lug  Brick  from  22%  to  24%. 
Three  inch  Vertical  Fiber  or  Wire-Cut-Lug-  Brick  from  24%  to  2&f/, . 
Two  and  one-half  inch   Vertical   Fiber  Brick  from  27%   to   32%. 
Four   inch   Repressed   Block   from   21%    to     24%. 
Four    inch    depth    Repressed   Brick    from    25%    to   30%. 


SPECIFICATIONS 


111 


REPORT  OF  STANDARD  RATTLER  TEST  OF  PAVING  BRICK 
IDENTIFICATION  DATA    (Serial  No ) 


Name  of  firm  furnishing  sample 

Name  of  the  firm  manufacturing  the  sample 

Street  or  job  which  sample  represents 

Brands  or  marks  on  the  brick 

Quantity    furnished    

Date   received   Date   tested 

Length  Breadth  Thickness. 

STANDARDIZATION  DATA 

Number  of   charges   tested   since   last   inspection 


Weight  of  Charge. 
(After  Standardi- 
zation) 


Ten  Large  Spheres 

Small  spheres 

..Total  weight  


Condition 
of  Lock- 
nuts  on 
Staves 


Condition  of 
Scales 


Number 
and  Position 

of  Fresh 
Stave  Liners 


Repairs. 
(Note  any 
repairs  affect- 
ing the  con- 
dition of  the 
barrel) 


Number  of  charges  tested  since  stave  linings  were  removed. 

RUNNING  DATA 

Time  Readings  Revolution       Running 

Counter  Notes, 

|    Hours        Minutes        Seconds         Readings       Stops,  etc. 

Beginning  of  Test 

Final  Reading 

WEIGHTS  AND  CALCULATIONS 

Percentage  Loss 

(Note:  The  Calculation 

Must  Appear 

Initial  weight  of  ten  bricks 

Final  weight  of  same , 

Loss  of  weight 

Number  of  broken  bricks  and  remarks  on  same 

I   certify   that   the   foregoing  test  was   made   under  the   speci- 
fications of and  is  a  true 

record. 

Date Signature    of    Tester 

Location  of  Laboratory  


112  SPECIFICATIONS 

HANDLING  OF  BRICK.  All  brick  shall  be  unloaded  from 
wagons  or  cars  by  clamps  and  neatly  piled  adjacent  to  the  work  be- 
fore the  grading  is  finished.  Under  no  circumstances  shall  brick  be 
thrown  from  wagons  to  piles  or  from  cars  to  wagons.  Brick  shall 
be  piled  where  they  will  not  be  spattered  with  dirt  and  mud.  When 
laying  brick  in  the  pavement,  they  shall  be  caried  from  the  piles 
to  the  pavers  with  clamps  or  on  pallets  or  by  suitable  conveyors. 
No  wheeling  in  barrows  will  be  allowed. 

ASPHALTIC  CEMENT.  Where  an  asphaltic  filler  for  the  brick 
is  specified,  the  asphaltic  cement  shall  conform  to  the  following  re- 
quirements: 

It  shall  be  free  from  water  or  decomposition  products. 

The  various  hydrocarbons  composing  it  shall  be  present  in 
homogenous  solution,  no  oily  or  granular  character  being  present. 
It  must  be  of  such  a  consistency  that  at  a  temperature  of  25°  C. 
a  No.  2  needle  weighted  with  100  grams  will  not,  in  five  (5)  seconds, 
penertate  more  than  iy2  millimeters.  The  exact  penetration  shall 
not  vary  more  than  0.4  millimeters  from  that  fixed  by  the  Engineer 
for  this  work  within  the  above  limits.  The  No.  2  needle  referred  to 
is  a  common  sewing  needle  about  1  millimeter  in  diameter  and  tap- 
ering uniformly  to  a  sharp  point  for  a  centimeter  of  its  length. 

At  0°C.,  a  No.  2  needle  weighted  with  200  grams  shall  penetrate 
in  one  minute  at  least  2  millimeters. 

At  45  °C.,  a  No.  2  needle  weighted  with  50  grams  shall  not  pene- 
trate in  5  seconds  more  than  11  millimeters. 

Fifty  grams  of  it  shall  not  lose  more  than  three  per  cent  (3%) 
in  weight  upon  being  maintained  at  a  uniform  temperature  of  165  °C. 
for  five  hours  in  a  cylindrical  vessel  two  and  three  sixteenths  (2  3/16) 
inches  in  diameter  and  one  and  three-eights  (1%)  inches  high,  and 
the  penetration  at  25 °C.  of  the  residue  must  not  be  less  than  one- 
half  the  penetration  of  the  original  sample  before  heating. 

The  melting  point  shall  not  be  less  than  80  °C.  and  not  more 
than  120  °C. 

It  shall  not  contain  more  than  four  and  one-half  per  cent 
(4y2%)  of  carbonaceous  matter  insoluble  in  chemically  pure  carbon 
bisulphide,  air  temperature. 

It  shall  be  soluble  in  85°  Baume  Petroleum  naphtha,  air  tem- 
perature, to  the  extent  of  not  less  than  65%  and  not  more  than 

85%. 

Its  solubility  in  carbon  tetrachloride  shall  not  be  more  than 
1%%  less  than  its  solubility  in  carbon  bisulphide,  both  tests  being 
made  at  air  temperature. 

Its  ductility,  at  a  temperature  of  25 °C.  shall  not  be  less  than 
one  centimeter.  Ductility  by  the  terms  of  this  contract,  shall  be 
understood  to  mean  the  distance  in  centimeters  that  a  cylinder  of 
the  asphaltic  cement,  one  centimeter  in  diameter,  can  be  drawn  out 
at  the  rate  of  one  centimeter  per  minute. 


SPECIFICATIONS  113 

The  drawing  out  shall  be  accomplished  by  means  of  two  similar 
clips  cylindrical  in  form,  of  inside  diameter  of  about  three  centime- 
ters, open  at  one  end,  and  having  a  concentric  orific  one  centime- 
ter in  diameter  through  a  circular  plate  not  more  than  0.5  millime- 
ters thick  and  covering  the  other  end.  To  make  a  determination,  one 
of  the  clips  is  placed  on  a  smooth  surface  with  the  open  end  down. 
The  other  clip  is  then  placed  on  top  of  the  first,  with  the  open  end 
up,  so  that  the  one-centimeter  orifices  coincide.  The  hot  asphaltic 
cement  is  poured  into  the  top  one  slowly  so  as  to  fill  both  clips 
completely.  The  temperature  of  the  asphaltic  cement  is  then  ad- 
justed to  the  temperature  of  25  °C.  and  the  clips  are  pulled  apart  at 
the  rate  of  one  centimeter  per  minute. 

EXPANSION  JOINT  MATERIAL.  Where  cement  grout  filler 
is  used  for  the  brick,  the  expansion  joint  material  shall  consist  of 
premoulded  asphalt  or  tar  cement  held  in  shape  by  paper,  fiber  or 
wool  felt  approved  by  the  Engineer. 

The  paving  joint  material  must  be  soft  and  pliable  at  32  de- 
grees F.  and  must  not  melt  or  flow  at  125  degrees  F. 

It  shall  be  of  the  thickness  specified  and  at  least  50  per  cent 
shall  be  pure  bitumen.  It  shall  be  the  full  depth  of  the  brick  in 
width  and  cut  into  lengths  that  can  be  conveniently  handled. 


114  SPECIFICATIONS 

CONSTRUCTION  OF  PAVEMENT 

SUB-GRADE 

EXCAVATION.  The  portion  of  the  roadway  indicated  upon 
the  plans  to  be  paved  shall  be  brought  by  excavating  or  filling,  as 
the  case  may  be,  from  the  present  surface  thereof  to  a  sub-grade 

which  when  properly  prepared,  shall  be 

( )   inches  below  the  established  grade  at  the  curb  or  gutter 

line  and  shall  conform  to  the  general  cross  section  of  the  sub-grade 
as  indicated  upon  the  plans,  except  at  such  point  or  points  where 
there  exists  a  difference  in  the  level  between  street  railway  tracks 
and  the  curbs,  or  between  the  opposite  curbs  themselves,  or  where 
proper  drainage  may  require  it,  then  the  surface  of  the  pavement 
may  be  lowered  or  raised  within  a  range  of  one  foot  as  the  Engi- 
neer may  direct. 

Earth  in  embankment  shall  be  placed  in  layers  not  more  than 
six  inches  in  thickness  and  each  layer  thoroughly  rolled.  When 
the  total  depth  of  embankment  is  one  foot  or  less,  the  original 
ground  surface,  if  it  is  grown  to  sod,  or  weeds,  or  is  hard  and  com- 
pacted, shall  be  plowed  so  that  the  added  new  soil  will  knit  to  the  old. 

No  allowance  shall  be  made  for  any  earth  placed  in  embank- 
ment except  that  which  is  obtained  from  a  source  other  than  the 
roadway  herein  provided  to  be  improved  and  then  at  the  contract 
price  per  cubic  yard  for  earth  embankment. 

EXCAVATED  MATERIAL.  All  cross  walks,  stone  flagging, 
old  paving  or  guttering,  which  may  be  suitable  for  use  by  the  City, 
shall  be  removed  by  the  contractor  and  deposited  uninjured  as 
directed  within  1,000  feet  of  the  place  of  excavation. 

Earth  or  other  material  excavated  in  addition  to  that  required 
for  filling  on  the  street  being  paved  shall  be  used  as  directed  by  the 
engineer  for  filling  and  grading  adjoining  streets  or  alleys  without 
extra  charge,  provided  that  the  haul  required  of  such  excavated 
material  shall  not  exceed  1,000  feet. 

The  contractor  shall  be  paid cents  per  cubic  yard 

for  each  100  feet  overhaul  for  distances  in  excess  of  1,000  feet. 

All  excavated  material  except  as  above  provided  shall  be  at 
the  disposition  of  the  contractor. 

ROLLING.  The  sub-grade  shall  be  thoroughly  rolled  with  a 
self-propelled  roller  weighing  not  less  than  two  hundred  and  fifty 
(250)  pounds  per  inch  of  face  of  roller.  Should  such  rolling  develop 
any  soft  or  spongy  ground  or  improperly  back-filled  excavation  for 
service  pipes  or  connections,  etc.,  the  same  shall  be  removed  and 
such  excavations  and  such  depressions  as  may  appear  shall  be  re- 
filled and  tamped  with  earth  or  broken  rock  acceptable  to  the 


SPECIFICATIONS  115 

Engineer,  and  the  entire  sub-grade  be  brought  to  an  even  and  com- 
pact surface  of  uniform  bearing  power  by  rolling  or  ramming.  Any 
damage  done  to  the  sub-grade  from  hauling  over  it  must  be  repaired 
before  concrete  is  deposited. 

DRAINAGE.  At  places  shown  on  the  plans  or  where  in  the 
opinion  of  the  Engineer,  drainage  of  the  sub-grade  is  necessary, 
first-class  drain  tiles  shall  be  laid  with  open  joints  on  a  firm  bed  to 
such  lines  and  grades  as  directed  by  the  Engineer,  not  less  than 
twelve  (12)  inches  below  the  finished  sub-grade  and  the  trench 
back-filled  with  clean  cinders  or  broken  stone.  The  drain  shall  be 
connected  to  the  nearest  catch  basin  or  other  outlet  in  such  manner, 
as  indicated  by  the  Engineer.  In  general  the  location  of  drains  will 
be  shown  on  the  plans  and  these  shall  be  paid  for  at  the  price  bid, 
but  when  during  construction  it  is  found  necessary  to  provide  drains 
not  shown  on  the  plans  for  the  proper  protection  of  the  pavement, 
the  price  paid  for  drain  tile,  in  place  complete,  shall  be  the  actual 
labor  and  material  cost,  plus  ten  (10%)  per  cent,  to  cover  overhead 
charges,  use  of  tools  and  profit. 

MOISTENING  OF  SUB-GRADE.  When  in  the  opinion  of  the 
Engineer,  the  sub-grade  after  rolling,  is  too  dry  to  properly  receive 
the  concrete  foundation,  it  shall  be  thoroughly  wet  far  enough  in 
advance  to  avoid  rnuddy  conditions  for  placing  concrete. 

TEMPLET  FOR  iSUB-GRADE.  The  sub-grade  shall  be  tested 
by  means  of  the  templet  hereinafter  described  to  insure  the  proper 
grade,  crown  and  depth. 


116  SPECIFICATIONS 


CONCRETE  FOUNDATION 

THICKNESS  OF  CONCRETE.  Upon  the  sub-grade  prepared 
as  above  described,  Portland  Cement  Concrete  shall  be  laid  to  a 

thickness  after  tamping  and  fininshing  of  not  less  than 

( )   inches,  the  upper  surface  of  which  shall  conform" to" a 

plane   parallel  with  and ( )    inches  below  the 

finished  surface  of  the  pavement. 

PROPORTIONS.  The  Portland  Cement  Concrete  for  the 
foundation  shall  be  composed  of  one  (1)  volume  of  cement,  three  (3) 
volumes  of  sand  and  six  (6)  volumes  of  broken  stone  or  gravel. 
Measurements  shall  be  by  volume  of  loose  materials  and  one  barrel 
of  cement  shall  be  taken  as  four  (4)  cubic  feet. 

Where  Flint  "chats"  are  used  for  the  coarse  aggregate  the  pro- 
portions shall  be  one  (1)  part  cement,  one  and  one-half  (iy2)  parts 
sand  and  (5)  parts  screened  Flint  "chats."  The  proportions  of  sand 
and  stone  may  be  varied  at  the  option  of  the  Engineer,  but  no  change 
will  be  allowed  which  will  affect  the  proportions  of  the  cement  to  the 
total  of  the  aggregate  as  specified. 

MIXING.  The  materials  for  concrete  shall  be  accurately  pro- 
portioned and  mixed  in  a  batch  mixing  machine  of  a  type  approved 
by  the  Engineer,  and  mixing  shall  continue  for  at  least  one-half  (%) 
minute  after  all  materials  are  in  the  drum.  The  drum  shall  be  com- 
pletely emptied  before  any  material  for  the  following  batch  is  added. 

The  materials  shall  be  mixed  wet  enough  to  produce  a  concrete 
of  such  consistency  that  it  will  flush  readily  when  tamped,  but  which 
can  be  handled  without  causing  a  separation  of  the  coarse  aggregate 
from  the  mortar,  and  whic.h  will  not  creep  toward  the  curb  or  sag 
out  of  place  when  deposited  and  lightly  tamped.  After  the  addi- 
tion of  water  the  mixture  shall  be  handled  rapidly  to  the  place  of 
final  deposit.  Under  no  circumstances  shall  concrete  be  used  that 
has  begun  to  set. 

Note — It  is  impossible  to  write  definite  specifications  for  mix- 
ing concrete,  particularly  to  fix  its  proper  consistency.  At  present  the 
best  evidence  for  determining  the  proper  consistency,  is  found  in  the 
nature  of  the  green  concrete  in  place.  Certain  facts,  however,  are 
definitely  established. 

With  any  given  proportion  of  the  aggregates  to  cement,  the 
strongest  concrete  is  obtained  when  the  aggregates  are  uniformly 
distributed  to  form  a  homogeneous  mass,  with  sufficient  water  to 
completely  hydrate  the  cement,  producing  a  concrete  readily  handled 
and  placed. 

An  excess  of  water  reduces  the  adhesion  of  the  cement  to  the 
fine  aggregate,  and  of  the  mortar  to  the  coarse  aggregate.  It  also 
produces  a  porous  concrete.  A  lack  of  water  prevents  hydration  or 
proper  setting  of  the  cement,  weakens  the  concrete,  and  lessens  the 
ease  of  handling  and  placing. 

DEPOSITING.  Immediately  prior  to  placing  the  concrete,  the 
sub-grade  shall  be  brought  to  an  even  compact  surface.  The  con- 
crete must  be  taken  from  the  machine  in  such  manner  as  will  insure 


SPECIFICATIONS  117- 

against  loss  of  mortar,  promptly  deposited  in  place  and  tamped  until 
it  has  been  thoroughly  compacted  for  its  full  depth  and  mortar  flushes 
to  the  surface. 

TEMPLET.  To  assist  in  bringing  the  surface  of  the  founda- 
tion to  correct  grade  and  crown,  the  Contractor  shall  furnish  a 
templet  extending  the  full  width  of  the  roadway,  where  the  pave- 
ment is  less  than  thirty  (30)  feet  wide,  and  one-half  (MO  the  width 
of  roadway  where  the  pavement  is  more  than  thirty  (30)  feet  wide, 
or  there  are  car  tracks  on  the  street.  This  templet  shall  be  con- 
structed in  a  manner  approved  by  the  Engineer  and  must  be  cut 
so  as  to  fit  accurately  the  upper  cross-sectional  surface  of  the  founda- 
tion as  shown  on  the  plans,  when  the  ends  of  the  templet  rest  on  the 
curb,  or  on  the  street  car  rail.  The  templet  shall  be  used  constantly 
to  insure  the  proper  thickness  of  concrete  is  being  placed  and  that 
the  finished  surface  conforms  to  the  proper  grade  and  crown  and  is 
free  from  depressions  and  inequalities.  The  concrete  shall  be  de- 
posited to  the  full  thickness  from  curb  to  curb  or  car  track  and 
finished  immediately  thereafter. 

FINISHING.  The  surface  finish  of  the  concrete  foundation 
shall  present  a  reasonably  smooth,  dense  appearance,  free  from  marked 
uneveness,  rock  pockets  or  other  defects  and  true  to  crown  and  grade. 

CONSTRUCTION  JOINTS.  When  concreting  is  stopped  at 
noon,  at  night  or  for  periods  of  more  than  thirty  minutes,  the  con- 
crete shall  be  finished  against  a  plank  extending  completely  across 
the  roadway  in  a  position  perpendicular  to  the  surface  of  the  finished 
pavement.  If  necessary,  in  case  of  a  break-down,  enough  concrete 
shall  be  mixed  by  hand  to  complete  the  concrete  foundation  up  to 
the  stop-plank.  Any  concrete  in  excess  of  that  necessary  to  com- 
plete the  foundation  to  the  stop-plank  shall  not  be  used  in  the  work. 
In  any  case,  great  care  must  be  used  in  tamping  and  spading  the 
concrete  against  the  stop-plank  so  that  there  will  be  no  rock  pockets 
when  the  plank  is  removed.  When  concreting  is  commenced  again, 
the  stop-plank  shall  be  removed  and  the  fresh  concrete  placed  di- 
rectly against  the  old  concrete.  The  same  care  must  be  taken  to 
avoid  rock  pockets  and  to  see  that  the  surfaces  of  the  old  and  new 
concrete  exactly  correspond. 

HEADERS.  Between  the  curb  lines  of  an  intersecting  street 
or  alley  that  is  unpaved  the  concrete  and  pavement  shall  be  finished 
against  a  white  oak  plank  two  (2)  inches  thick  and  twelve  (12) 
inches  deep  and  of  such  length  as  the  Engineer  may  designate. 
The  plank  shall  be  securely  spiked  to  stout  oak  staves  driven  well 
into  the  ground  and  backed  with  sufficient  concrete  to  hold  it  in 
place.  The  upper  edge  of  the  plank  shall  be  neatly  adzed  off  to 
conform  to  the  finished  surface  of  the  pavement.  Where  the  work 
adjoins  any  pavement  already  laid,  the  Engineer  may  require  the 
contractor  to  remove  and  relay  a  sufficient  quantity  of  the  old 
pavement  to  form  a  satisfactory  junction  of  the  two  pavements. 

The  concrete  shall  extend  close  up  to  all  openings,  manholes, 
catch  basins,  etc.,  and  be  finished  about  the  same  in  a  neat  and  work- 
manlike manner. 


118  SPECIFICATIONS 

CURING  AND  PROTECTING.  As  soon  as  the  concrete  in  the 
foundation  has  become  hard  enough  to  prevent  pitting  it  shall  be 
sprayed  with  water  and  shall  be  kept  wet  for  a  period  of  five  (5) 
days  thereafter.  This  work  must  be  thoroughly  done  and  to  the  sat- 
isfaction of  the  Engineer.  During  rainy  weather  or  when  the  aver- 
age daily  temperature  is  below  fifty  (50)  degrees  Fahrenheit,  per- 
mission may  be  obtained  from  the  Engineer  to  omit  the  sprinkling. 

The  contractor  shall  erect  and  maintain  suitable  barricades 
and  provide  watchmen  to  protect  the  concrete  from  traffic  and  any 
part  of  the  foundation  damaged  by  traffic  or  other  causes  during  the 
curing  period  shall  be  repaired  or  replaced  in  a  manner  satisfactory  to 
the  Engineer. 

Under  the  most  favorable  conditions  for  hardening  in  hot 
weather,  the  wearing  surface  shall  not  be  placed  on  the  foundation 
for  at  least  seven  (7)  days  and  in  cool  weather  for  an  additional  time 
as  required  by  the  Engineer. 

Concrete  shall  not  be  mixed  or  deposited  when  the  temperature 
is  below  freezing.  In  no  case  shall  concrete  be  deposited  upon  a 
frozen  sub-grade. 

CEMENT-SAND  BED.  Upon  the  concrete  foundation,  which 
has  previously  been  cleaned,  there  shall  be  spread  a  layer  of  sand 
and  Portland  Cement  mixed  in  the  proportion  of  one  (1)  part 
cement  to  four  (4)  parts  sand.  The  cement  and  sand  shall  be  mixed 
dry  until  the  mixture  has  a  uniform  color  throughout  and  shall  be 
spread  on  the  foundation  dry  not  less  than  three-quarters  (%)  inch 
in  thickness,  the  depth  being  made  as  nearly  uniform  as  possible 
and  averaging  one  inch,  sufficient  to  cover  all  high  points  or  pro- 
truding rock  in  the  foundation  and  provide  a  uniform  bedding  course 
for  the  brick. 

The  cement-sand  bed  shall  be  carefully  shaped  to  the  true 
cross  section  of  the  roadway  by  means  of  a  properly  made  templet. 

At  intersections  or  where  the  pavement  is  to  be  warped,  and 
a  templet  is  impractical,  the  use  of  lutes  will  be  permitted. 

The  bedding  or  cushion  course  shall  be  prepared  at  least  20 
feet  in  advance  -of  the  bricksetters,  but  the  brick  shall  be  laid, 
rolled  and  culled  as  soon  after  mixing  the  dry  cement  and  sand 
as  practical. 


SPECIFICATIONS  119 


THE  WEARING  SURFACE 

LAYING  THE  BRICK.  In  delivering  the  brick  from  the  piles 
for  placement  in  the  streets,  no  wheeling  in  barrows  will  be  allowed 
on  the  brick  surface,  but  they  should  be  carried  on  pallets  or  carriers 
in  such  order  that  when  delivered  to  the  dropper,  they  will  lie  in  such 
a  position,  that  each  brick,  in  the  regular  operation  of  placing  it  upon 
the  superfoundation  as  prepared,  will  bring  the  projections  in  the 
same  direction  and  the  better  edge  uppermost. 

For  closures  nothing  less  than  three  (3)  inch  bats  shall  be  used 
with  the  fractured  edges  laid  toward  the  center  of  the  pavement,  a 
piece  being  cut  off  of  the  adjacent  whole  brick  if  necessary  to  make 
a  three  (3)  inch  closure  space.  Broken,  chipped  or  warped  brick 
not  suitable  to  lay  as  a  whole  shall  be  used  for  closures  and  bats  as 
far  as  practicable.  All  joints  shall  be  broken  at  least  three  (3) 
inches.  No  course  shall  deviate  from  a  straight  line  more  than  two 
(2)  inches  in  thirty  (30)  feet.  All  brick  when  laid  shall  be  clean  and 
kept  clean  until  the  filler  is  applied.  When  conditions  of  the  ground 
are  such  that  mud  would  be  tracked  or  carried  onto  the  pavement, 
the  work  of  laying  the  brick  will  not  be  allowed. 

ALONG  STREET  CAR  TRACKS.  Along  street  car  tracks  the 
brick  must  not  be  laid  within  one-quarter  (%)  of  an  inch  of  the 
rail  and  when  rolled  shall  be  one-quarter  (^4)  of  an  inch  below  the 
top  of  the  rail.  The  space  between  the  web  of  the  rail  and  the  brick 
shall  be  filled  with  cement  mortar  made  in  the  proportions  of  one 
(1)  part  Portland  Cement  and  three  (3)  parts  sand.  The  mortar 
shall  be  packed  against  the  rail  and  cut  off  to  a  true  surface  before 
the  brick  are  laid. 

EXPANSION  JOINTS.  When  Portland  Cement  grout  is 
specified  to  be  used  as  a  joint  filler,  expansion  joints  shall  be  placed 
parallel  with  and  at  each  of  the  curb  lines.  The  premoulded  ex- 
pansion joint  strips  of  the  proper  thickness  and  width  shall  be  set 
against  the  curb  in  advance  of  the  laying  of  the  brick  and  the  brick 
laid  against  this,  care  being  taken  to  have  the  separate  strips  close 
butted  and  set  the  full  depth  of  the  brick.  For  roadways  less  than 
thirty-six  (36)  feet  in  width,  the  expansion  strip  along  each  curb 
shall  be  three-quarters  (%)  of  an  inch  thick,  and  for  roadways  of 
greater  width,  one  (1)  inch  in  thickness. 

ROLLING.  After  the  brick  in  the  pavement  have  been  passed 
for  rolling  and  the  surface  swept  clean,  the  pavement  shall  be  rolled 
with  a  self-propelled  roller  weighing  not  less  than  three  (3)  nor  more 
than  five  (5)  tons,  in  the  following  manner:  The  brick  next  the  curb 
shall  be  tamped  with  a  hardwood  tamper  to  the  proper  grade.  The 
rolling  shall  then  commence  near  the  curb  at  a  very  slow  pace  and 
continue  back  and  forth  toward  the  center  until  the  center  of  the 


120  SPECIFICATIONS 

street  is  reached;  then  passing  to  the  opposite  curb,  it  shall  be  re- 
peated in  the  same  manner  to  the  center  of  the  street.  Each  back- 
ward passage  of  the  roller  shall  cover  the  same  path  as  the  corres- 
ponding forward  passage  and  each  portion  of  the  pavement  shall  re- 
ceive enough  even  passages  of  the  roller  to  imbed  each  brick  firmly, 
evenly  and  to  a  uniform  bearing  in  the  bedding  course. 

The  pavement  shall  then  be  rolled  transversely  at  an  angle  of 
forty-five  (45)  degrees  from  curb  to  curb,  repeating  the  rolling  in 
the  opposite  forty-five  (45)  degree  direction.  Before  and  after  this 
transverse  rolling  has  taken  place,  all  broken  or  injured  brick  must 
be  taken  up  and  replaced  with  perfect  ones.  The  substitute  brick 
must  be  brought  to  the  true  surface  by  tamping. 

After  final  rolling  the  pavement  shall  be  tested  with  a  six  (6) 
foot  straight  edge,  laid  parallel  with  the  curb,  and  any  depressions 
exceeding  one-quarter  (%)  of  an  inch  must  be  taken  out.  If  neces- 
sary, the  pavement  shall  be  again  rolled. 

ASPHALT  FILLER.  Where  asphalt  filler  is  specified,  the 
surface  of  the  brick  after  they  have  been  rolled  and  culled  shall  be 
swept  clean,  and  the  filler  shall  be  applied  as  soon  after  the  rolling 
as  possible.  All  brick  shall  be  filled  and  completed  on  the  day  on 
which  they  are  laid. 

The  asphaltic  cement  shall  be  heated  in  a  suitable  kettle  equip- 
ped with  a  thermometer,  which  will  register  the  temperature  of  the 
contents  at  all  times.  The  asphaltic  cement  shall  at  no  time  be 
heated  to  a  greater  temperature  than  its  flash  point  nor  poured  at  a 
temperature  of  less  than  three  hundred  (300)  degrees  F.  In  order 
to  insure  that  the  filler  will  adhere  firmly  to  the  brick  they  shall  be 
clean  and  thoroughly  dry.  The  filler  shall  be  moved  slowly  back 
and  forth  over  the  surface  by  means  of  suitable  squeegees  until  all 
the  joints  are  completely  filled  and  the  surface  entirly  covered  with 
a  thin  coating.  Sufficient  time  shall  be  allowed  after  the  asphaltic 
cement  is  flushed  over  the  surface  before  using  the  squeeges  to 
allow  it  to  penetrate  to  the  bottom  of  the  joints.  Care  must  be 
taken  not  to  squeegee  partially  cooled  asphaltic  cement  over  un- 
covered brick  thereby  bridging  the  top  of  the  joint  and  not  filling 
the  bottom.  All  settlement  in  the  joints  after  the  asphalt  has  cool- 
ed shall  be  corrected  by  adding  filler  before  placing  the  top  dressing. 

A  coating  of  dry,  clean  "chats"  passing  a  No.  8  screen  or  sand 
shall  then  be  uniformly  spread  over  the  surface  to  take  up  the  sur- 
plus asphalt.  The  chats  or  sand  shall  preferably  be  heated  to  250 
degrees  F.  The  pavement  shall  then  be  thoroughly  rolled  to  imbed 
the  surface  dressing  in  the  asphalt.  After  this  rolling  the  pavement 
may  be  thrown  open  to  traffic.  Additional  material  shall  be  added 
or  any  surplus  swept  up  and  removed  as  directed  by  the  Engineer 
any  time  within  ten  (10)  days  after  traffic  is  allowed  over  the  pave- 
ment. 

CEMENT  GROUT  FILLER.  The  filler  shall  be  composed  of 
one  and  one-half  (l1^)  parts  of  fine,  clean,  sharp  sand  and  one  (1) 


SPECIFICATIONS  121 

part  Portland  Cement.     The  sand  shall  be  measured  in  a  box  having 
the  same  cubical  contents  as  one  sack  of  cement. 

Before  any  grouting  is  done,  a  sufficient  amount  of  cement  and 
the  proper  amount  of  sand  to  complete  the  work  prepared  for  grouting 
at  that  time,  but  not  to  exceed  one-half  (l/2)  day's  run  shall  be  thor- 
oughly mixed  dry  until  the  mass  assumes  a  uniform  color.  From 
this  mixture  an  amount  not  exceeding  two  (2)  cubic  feet  shall  be 
taken  and  placed  in  the  grouting  box  and  water  slowly  added  until  a 
grout  that  will  penetrate  to  the  bottom  of  the  brick  is  obtained. 
From  the  time  the  water  is  applied  until  all  is  removed  and  floated 
into  the  joints  of  the  pavement  the  mixture  must  be  kept  in  constant 
motion.  A  mechanical  mixer  approved  by  the  Engineer  that  will 
meet  these  requirements  may  be  used  after  the  dry  mixture  of 
sand  and  cement  has  been  made.  Before  the  grout  is  applied  the 
brick  shall  be  thoroughly  wet  by  being  gently  sprayed. 

The  water  shall  be  added  to  this  dry  mixture  in  a  box  prefer- 
ably about  four  (4)  feet,  eight  (8)  inches  long,  thirty  (30)  inches  wide, 
and  fourteen  (14)  inches  deep,  resting  on  legs  of  different  lengths, 
so  that  the  mixture  will  rapidly  flow  to  the  lower  corner  of  the  box, 
the  bottom  of  which  shall  be  about  three  (3)  inches  above  the  pave- 
ment. One  box  shall  be  used  for  each  fourteen  (14)  feet  in  width 
of  roadway,  and  at  least  two  (2)  boxes  must  be  used  in  all  cases. 

The  grout  shall  be  removed  from  the  box  with  scoop  shovels 
and  applied  to  the  brick  in  front  of  the  sweepers,  who  shall  rapidly 
sweep  it  lengthwise  of  the  brick  into  the  unfilled  joints,  until  the 
joints  are  filled  to  within  not  more  than  one-half  (%)  in.  of  the  top 
of  the  brick.  After  the  grout  has  had  a  chance  to  settle  into  the 
joint  and  before  the  initial  set  developes,  the  balance  of  every  joint 
shall  be  filled  with  a  thicker  grout,  and,  if  necessary,  refilled,  until 
the  joints  remain  full  to  the  top. 

After  this  application  has  had  time  to  settle  and  before  the 
initial  set  takes  place,  the  pavement  shall  be  finished  to  a  smooth 
surface  with  a  squeegee  or  wooden  scraper  having  a  rubber  edge, 
which  shall  be  worked  diagonally  over  the  brick. 

The  contractor  must  provide  thin  metal  strips  about  one-six- 
teenth (1/16)  inch  by  six  (6)  inches  by  three  (3)  feet  and  insert 
the  same  in  the  brick  just  across  the  roadway  when  closing  up  a 
stretch  of  grouting  at  work  intervals  so  that  the  grouting  will  end 
in  a  vertical  joint.  These  strips  must  be  taken  out  when  the  grout 
becomes  stiff  and  before  the  final  set. 

When  completed  and  the  cement  has  received  its  initial  set, 
the  pavement  shall  be  covered  with  a  one-half  (%)  inch  layer  of 
sand  or  loam,  which  shall  be  frequently  sprinkled  in  warm  weather. 
No  travel  shall  be  permitted  on  the  pavement  for  a  period  of  at 
least  seven  (7)  days  after  grouting,  or  longer,  as  the  Engineer  may 
require  on  account  of  weather  conditions. 

Ample  barricades  and  watchmen  shall  be  provided  by  the  con- 
tractor for  the  proper  protection  to  the  grouting. 


122  SPECIFICATIONS 

MALNTE NANCE.  During  the  period  for  which  the  pavement 
is  guaranteed  by  the  contractor,  he  shall  maintain  in  order  the  grade 
and  surface  of  all  the  aforesaid  work  and  make  all  repairs,  which 
may  be  necessary  from  any  imperfections  in  the  work  or  material 
or  from  any  crumbling  or  disintegration  of  the  pavement  materials. 
He  shall  make  good  to  the  satisfaction  of  the  Engineer  any  cracks, 
bunches,  holes  or  depressions  that  hold  water  or  that  measure  more 
than  one-half  (y2)  inch  from  the  underside  of  a  straight  edge,  six 
(6)  feet  long,  laid  on  the  surface  of  the  pavement.  The  contractor 
shall  make  good  any  settlement  due  to  improperly  prepared  or 
defective  sub-grade,  including  sunken  places  on  account  of  ftny 
trenches  or  holes  made  in  the  street  by  any  corporation  or  private 
party  prior  to  the  laying  of  the  pavement. 


SPECIFICATIONS  123 


MONOLITHIC 
BRICK  PAVEMENT 

DESCRIPTION.  In  Monolithic  Brick  Pavement  the  cushion 
or  bedding  course  between  the  concrete  foundation  and  the  brick 
wearing  surface  is  omitted  and  the  brick  are  imbedded  directly 
on  the  fresh  unset  concrete  covered  with  a  cement  sand  coating.  The 
joints  are  immediately  filled  with  Portland  Cement  grout  making  one 
solid  or  monolithic  slab  of  the  foundation  and  wearing  surface. 
Slabs  made  in  this  way  and  tested  as  a  beam  show  that  the  two 
parts  of  the  pavement,  the  foundation  and  the  brick  wearing  sur- 
face, act  as  a  unit  with  strength  proportional  to  the  total  depth 
of  the  concrete-brick  slab,  as  is  the  case  in  any  homogeneous  material. 

This  method  of  construction  has  been  used  most  successfully 
on  country  highways,  although  with  slight  modifications  it  has  been 
used  on  wide  city  streets.  The  success  of  the  whole  construction 
depends  on  obtaining  an  absolutley  true,  even  surface  to  the  con- 
crete foundation  so  that  the  brick  may  be  laid  while  the  concrete 
is  fresh  and  rolled  down  to  a  complete  and  uniform  bed  and  even 
surface.  This  is  more  difficult  of  accomplishment  on  many  city 
streets  where  warps  to  meet  catch  basins  and  special  conditions  are 
frequent  than  on  a  country  road  which  is  commonly  uniform  in 
width  and  crown  throughout  its  length.  Since  the  monolithic  brick 
pavement  is  stronger  for  the  same  depth  than  the  sand  cushion 
method  of  block  pavement  construction,  the  ordinary  thickness  of 
foundation  and  the  brick  wearing  surface  may  be  reduced  somewhat. 
A  three  (3)  inch  concrete  foundation  combined  with  a  good  quality 
two  and  one-half  (2%)  inch  depth  brick  should  be  as  strong  and 
satisfactory  as  a  four  (4)  inch  concrete  foundation,  one  (1)  inch 
sand  cushion  and  three  (3)  inch  depth  brick.  The  five  and  one-half 
('5%)  inch  monolithic  brick  pavement  is  probably  the  practical  min- 
imum where  the  pavement  is  laid  on  the  dirt  sub-grade.  No  curb 
edging  is  required  on  monolithic  road  paving.  All  of  these  items 
make  the  pavement  construction  very  economical  without  detracting 
from  its  strength  and  wearing  qualities. 


124  SPECIFICATIONS 


SPECIFICATIONS  FOR  MONOLITHIC 
BRICK  PAVEMENT 

The  specifications  on  the  preceding  pages  for  materials  to  be 
used  in  brick  pavements  should  govern  where  applicable. 

The  size  of  the  largest  piece  of  coarse  aggregate  for  concrete 
must,  however,  not  be  more  than  two  (2)  inches  in  diameter  and 
should  be  reduced  to  one  (1)  or  one  and  one-half  (l1^)  inches  if 
the  foundation  is  less  than  four  (4)  inches  in  thickness. 

The  excavation,  drainage  and  preparation  of  the  sub-grade  shall 
be  the  same  as  specified  for  brick  pavement.  The  thinner  the 
foundation  used,  the  greater  must  be  the  care  in  preparing  the  sub- 
grade. 

The  clauses  regarding  thickness  of  concrete,  proportions  and 
mixing  concrete  shall  be  same  as  specified. 

FORMS.  Where  no  curbing  is  provided,  stout  forms,  prefer- 
ably of  steel,  shall  be  set  and  securely  braced  along  both  sides  of  the 
proposed  pavement  so  that  the  top  edge  will  conform  to  the  line 
and  grade  of  the  top  edge  of  the  finished  brick  pavement,  with  the 
bottom  on  or  below  the  surface  of  the  sub-grade. 

DEPOSITING.  Immeditely  prior  to  placing  the  concrete  the 
sub-grade  shall  be  brought  to  an  even  compact  surface  and  wet 
down  as  heretofore  provided.  The  concrete  must  be  taken  from 
the  machine  in  such  manner  as  will  insure  against  loss  of  mortar, 
promptly  deposited  in  place  and  tamped  until  it  has  been  thoroughly 
compacted  for  its  full  depth  and  mortar  flushes  to  the  surface. 

In  placing  the  concrete,  workmen  will  be  guided  by  a  light 
wood  templet  resting  on  the  side  forms  and  so  made  as  to  leave  the 
concrete  a  little  in  excess  of  the  depth  required. 

Over  this  shall  be  drawn  a  specially  constructed  steel  templet 
consisting  of  a  six  (6)  inch  I-beam  in  front  and  a  six  (6)  inch  channel 
beam  in  the  rear  with  the  flanges  turned  back,  bent  true  to  the  crown 
or  cross  section  of  the  pavement  and  placed  in  a  frame  so  that  they 
will  be  rigidly  held  about  two  (2)  feet  apart.  The  templet  shall 
be  supported  on  two  (2)  rollers  at  each  end  resting  on  the  side 
forms.  The  first  section  or  I-beam  shall  be  three-sixteenths  (3/16) 
inch  lower  than  the  channel  beam  and  cut  the  concrete  base 
practically  to  a  true  surface,  which  shall  be  the  depth  of  the  brick 


SPECIFICATIONS  125 

to  be  used  below  the  finished  grade  of  the  pavement.  In  between 
these  beams  must  be  kept  a  sufficient  quantity  of  dry  mixed  Port- 
land Cement  and  sand  in  the  proportions  of  one  (1)  part  cement  to 
three  (3)  parts  sand.  The  rear  templet  distributes  this  thin  coat- 
ing of  dry  mortar  over  the  surface  of  the  base  leaving  the  surface 
entirely  smooth.  A  well  built  and  properly  operated  templet  is 
one  of  the  essentials  of  this  type  of  pavement.  Any  other  form  of 
templet  which  is  approved  by  the  Engineer,  and  will  give  the  sur- 
face finish  to  the  concrete  required,  may  be  used. 

LAYING  THE  BRICK,  Upon  the  foundation,  as  prepared, 
shall  be  laid  the  brick  before  the  concrete  in  it  has  had  an  oppor- 
tunity to  set.  The  brick  shall  be  carried  to  the  brick  setters  by 
conveyors,  on  pallets,  or  in  clamps  after  first  being  placed  for  delivery 
to  the  setter,  in  such  order  that  each  brick  in  the  regular  operation 
of  placing  has  the  lugs  in  the  same  direction  with  the  best  face 
uppermost.  The  brick  setters  will  stand  on  the  brick  already  laid, 
but  boards  shall  preferably  be  placed  for  the  brick  carriers  to  walk 
on.  iWheeling  in  barrows  over  the  freshly  laid  brick  will  not  be 
allowed. 

ROLLING.  After  the  brick  in  the  pavement  have  been  in- 
spected and  the  surface  swept  clean,  the  pavement  shall  be  rolled 
with  a  hand  roller  not  less  than  thirty  (30)  inches  long,  made  in 
sections  and  weighing  not  less  than  fifteen  (15)  nor  more  than  twenty 
(20)  pounds  per  inch  of  length.  The  rolling  must  be  kept  close  to 
the  laying  and  continued  until  the  brick  are  uniformly  bedded 
and  the  surface  is  smooth.  Portions  of  the  pavement  inaccessible 
to  the  roller  shall  be  tamped  by  use  of  hand  tampers  applied  upon 
a  short  piece  of  plank  two  (2)  inches  thick.  After  the  final  rolling, 
the  surface  shall  be  tested  with  a  ten  (10)  foot  straight  edge,  laid 
parallel  to  the  sides  and  any  depressions  or  humps  exceeding  one- 
quarter  (^4)  of  an  inch  must  be  taken  out. 

The  inspector  shall  keep  the  brick  culled  and  the  contractor 
shall  make  the  necessary  changes  and  replacements  so  that  the  work 
at  all  times  shall  be  ready  for  grouting  within  twenty-five  (25)  feet 
of  the  brick  laying. 

CEMENT  GROUT  FILLER.  As  soon  as  the  brick  have  been 
passed  for  filling,  Portland  Cement  grout  shall  be  applied  and  the 
joints  entirely  filled  as  specified  under  "Brick  Pavement." 

The  pavement  will  be  barricaded  and  the  grout  filler  cured  as 
specified  under  "Brick  Pavement." 

FINISHING  DAY'S  WORK.  The  concreting  work  will  be 
stopped  so  that  all  the  foundation  may  be  covered  with  brick  and 
grouted  by  the  end  of  the  day's  work.  The  concrete  shall  be  finished 
against  a  vertical  stop  plank  placed  transversely  to  the  roadway  in 
the  manner  specified  under  "Brick  Pavement,"  and  the  brick  laid, 
rolled  and  culled  up  to  this  plank.  The  grouting  shall  be  stopped 


126  SPECIFICATIONS 

five  (5)  or  six  (6)  rows  back  from  this  plank  by  inserting  the  metal 
strips  previously  described. 

On  beginning  work  again,  the  ungrouted  rows  of  brick  will  be 
carefully  removed,  leaving  the  foundation  bare  so  that  the  double 
steel  templet  may  be  backed  over  it  in  position  for  the  I-beam  to 
start  leveling  the  first  of  the  fresh  concrete  placed. 

The  brick  removed  will  then  be  carefully  replaced  in  the  same 
positions  they  formerly  occupied,  and  the  laying,  rolling  and  grout- 
ing proceed  as  before. 


Designs     and     Engravings     by 
BAIRD    COMPANY    ENGRAVERS 

Kansas      City,     Missouri 

Printed      and      Bound       by 
TINGLE-TITUS  PRINTING  COMPANY 

Kansas      City,       Missouri 


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